Course manual: National training on cage culture of seabass, 14-23 December 2009

Imelda Joseph

Introduction Mariculture has great potential in augmenting fish and shellfish production and food supply, creating employment possibilities and high potential for export. Cage farming could be considered the main system to facilitate the rapid growth of marine fish farming. It has ...

Aquaculture is the production of aquatic organisms i.e. fish, crustaceans, mollusc, aquatic plants, algae, etc. It is currently the fastest growing livestock industry in the world (FAO, 2009; Ozigboet al., 2014). Fish production could be carried out in a controlled environment like concrete or earthen ponds, vats made of wooden or fibre glass and plastics tanks or bowls. In many countries including Nigeria, aquaculture is currently limited to fish production because farmers have limited knowledge of other aquatic organisms and low production capacity. Nigeria is blessed with thirty-three billion cubic meters of water. The country’s fish demand is close to 1,000,000 tons. Aquaculture production is about 200,000 tons and domestic catch from rivers and lakes is about 450,000 tons. The gap in the demand and supply is being met through importation. Due to insufficiency of domestic production, importation of fish and fish products accounts for more than half of fish supply in the country. Fish farming, according to Olaoyeet. al., (2012) implies some sort of intervention in the rearing process to enhance production, such as regular stocking, feeding, protection from predators, etc. Aquaculture has the potential to become a sustainable practice that can supplement capture fisheries, eliminate fish importation and significantly contribute to feeding the world’s growing population. Fish production is a good source of employment, food security, income generation, from local and foreign exchange, ecotourism and improve health. Some of the major challenges hindering fish production are lack of technical knowhow on appropriate methods of fingerlings production, method of production of cheap local fish feed using available feed stuff and lack of simple reference materials that can serve as a guide since extension agents are not available. Fish production should not fail because there is huge market for fish. However, poor location of farm, inappropriate fish pond design and construction, poor technical knowhow and facilities, insecurity, poor supervision and inadequate fund to run farms are the reasons why many fish farms have failed. This handbook was written to provide basic information in these areas so that fish production could be a mean of livelihood and sustenance. The hand book is divided into ninesections to cover the core areas of fish production. The sections are biology of fish, artificial propagation of fish/induced breeding, pond construction and management, integrated fish farming, Ornamental fisheries, fish nutrition, fish genetics and fish diseases and health management. Basic technical words are explained in the glossary to help the understanding of trainees.

Fish production was previously heavily dependent upon capture fishery and in particular the marine resources. However, the capture fishery cannot be expected to be a perennial protein donor. Moreover, a substantial portion of the marine catch is being utilized for making industrial products which are not directly consumed by man. Therefore, a viable alternative by which fish production could be increased through a popularized bio technique, called aquaculture. Aquaculture may be defined as the “farming and husbandry of economically important aquatic animals and plants under controlled conditions”. The aquaculture sector is indeed remarkable for its diversity in operations, encompassing a very wide range of farming practices, species, environments and production systems, often with very distinct resource use patterns. The sector is also highly fragmented, ranging from smallholder ponds or cages providing a few kilos of fish per year to international companies with annual turnover in ...

Course Manual NATIONAL TRAINING ON CAGE CULTURE OF SEABASS 14 - 23 December 2009 Central Marine Fisheries Research Institute (Indian Council of Agricultural Research) Post Box 1603, Ernakulam North P.O., Kochi - 682 018, Kerala, India and National Fisheries Development Board Ministry of Agriculture, Government of India Blocks 401-402, Maitri Vihar, HUDA Commercial Complex Ammerpet, Hyderabd - 500 038, Andhra Pradesh, India Organizing Committee Course Coordinator Dr. Imelda Joseph Course Manual National Training on Cage Culture of Seabass Senior Scientist Mariculture Division Committee Members Dr. Shoji Joseph Published by Dr. G. Syda Rao Director Central Marine Fisheries Research Institute Kochi – 682 018, India Edited by Dr. Imelda Joseph Edwin Joseph, V. Susmitha, V. Senior Scientist Mariculture Division Dr. Boby Ignatius Senior Scientist Mariculture Division Shri K.M. Venugopalan Senior Technical Assistant Marine hatchery Shri C.N. Chandrasekharan P.A., FEMD/MD December 2009 Shri T.V. Shaji Skilled Support Staff Mariculture Division Printed at Nissema Printers Shri M.D. Suresh Skilled Support Staff Mariculture Division Smt Susmitha V. SRF, Mariculture Division Citation Example: Kandan, S. 2009. Commercialization of Asian Seabass Lates calcarifer as a candidate species for cage culture in India. In: Course manual: National Training on Cage Culture (Ed. Imelda Joseph et al.), Central Marine Fisheries Research Institute, December 14-23, 2009, Cochin, pp. 13-16. FOREWORD The culture of aquatic organisms in confined enclosures or “cage aquaculture” has grown tremendously during the past 25 years all over the world. Cage culture is presently undergoing great innovations in response to globalization and the growing demand for aquatic products. It has been predicted that the fish consumption in developing and developed nations will increase by 57 percent and 4 percent, respectively over the coming 10 years. Population growth, increased level of affluence and fast urbanization in developing countries are leading to major changes in supply and demand for animal protein, from both livestock and fish. In India it has become imperative to identify new and suitable sites for aquaculture and ocean is the limit. Cage culture is accessing and expanding into new untapped open-water culture areas such as lakes, reservoirs, rivers and coastal brackish and marine inshore and offshore waters. Moreover, there is a growing awareness that the possibilities offered by cage aquaculture have only begun to be explored in India. Cage culture offers not only production of food fish, but also it forms an alternative to conventional land based hatcheries, nurseries and even for rearing broodstock fishes in a more natural environment. It can also be employed for rearing of oceanic fishes like tuna and the most sought after crustaceans like lobsters. Within the Fisheries Division of the Indian Council of Agricultural Research (ICAR), the Central Marine Fisheries Research Institute (CMFRI), Kochi, is responsible for all programmes related to development of mariculture. CMFRI has initiated many successful mariculture activities including breeding and culture of edible oysters, pearl oysters, mussels, marine ornamental fishes, sea cucumbers, etc. At present as another feather in its cap, CMFRI has pioneered in introducing successful open sea cage culture of Asian seabass and lobsters at different locations in India. Keeping this in focus, the Institute has organized this National Training for the benefit of the farmers, researchers and extension officers representing all the maritime states in India, with a view to disseminate and share the information and experience in this emerging field of mariculture, in order to enhance their competency and confidence in the area. I am grateful to National Fisheries Development Board (NFDB), Hyderabad, for sponsoring the programme. I express my gratitude to Dr. (Mrs.) Imelda Joseph, Course Coordinator and other committee members for organizing the programme in a befitting manner. I thank all the faculty members from CMFRI and other organizations like CIBA, CIFT and MPEDA. I take this opportunity to place on record my sincere appreciation for the whole-hearted cooperation extended by the administrative, technical and auxilliary staff of the Institute who have also contributed towards the organization of the training. I am confident that the participants would greatly benefit from this training. 14th December 2009 Dr. G. Syda Rao Director PREFACE Aquaculture aims at producing aquatic organisms of nutritional, ornamental, therapeutic and industrial value. Cage culture is one avenue where immense scope is there for all these. Cage culture is impressive to adopt in the fact that it provides ownership in public water with less cost of construction and reduced capital investment, safety from predators and competitors and ultimately high yield of fish with good economic returns. The manual being released on this occasion contains the lecture notes presented by the faculty. On this occasion I have great pleasure to record my whole-hearted appreciation to all my committee members for their sincere and dedicated work. Dr. G. Syda Rao, Director, CMFRI, has extended all the possible cooperation and guidance in organizing the Training Programme for which I am grateful to him. I am grateful to Dr. Shoji Joseph and Dr. Boby Ignatius, Senior Scientists, Mariculture Division, for their continued support in looking after the various academic and other field programmes. My thanks are due to Dr. A. P. Lipton, Principal Scientist, Vizhinjam RC of CMFRI, for making the arrangements for the field visit to cages in Kanyakumari district. I am grateful to Shri K. M. Venugopalan, Technical Staff, Marine Hatchery, for assisting in the field work as well as in the conduct of the training programme. I have great pleasure to extend my thanks to Mrs. Susmitha, V., Tijo Varghese and Anu Mathew, Senior Research Fellows, for their sincere and devoted assistance in the various facets of organizing the training. The field support by Shri M. D. Suresh and Shri T. V. Shaji, Skilled Supporting Staff, cannot be ignored on this occasion. My thanks are also due to all the faculty members and invited speakers. I also express my sense of gratitude to the HRD Cell, CMFRI, for their support in the conduct of the training. I place on record my sincere thanks to National Fisheries Development Board (NFDB), Hyderabad, for sponsoring the training programme. I am grateful to Mr. Edwin Joseph, Librarian, CMFRI, for his dedicated contribution for the lay out and printing of this manual in time. I thank Dr. G. Gopakumar, Head, Mariculture Division, for being a motivation in conduct of this training, Dr. Grace Mathew, Head in Charge FEM Division, for her support, other Heads of Divisions at CMFRI, Scientist colleagues and friends. My sincere thanks are also due to the administrative and auxilliary staff and research scholars, who have extended their help. I am sure that the manual released on this occasion would enable the participants to enhance their knowledge and competence in the field of Cage culture. 14th December 2009 Imelda Joseph Senior Scientist & Course Coordinator RESOURCE PERSONS Sl. No. 1 Name and Designation Office Address Dr. Syda Rao, G. Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P. O. Kochi – 682 018, Kerala Director, CMFRI 2 Dr. Gopakumar, G. Head, MCD 3 Dr. Thirunavukkarasu, A. R. Head, Fish Culture Division 4 Dr. Sathiadhas, R. Head, SEETTD 5 Dr. Grace Mathew Head in-charge, Mariculture Division 6 Dr. Saly N. Thomas Senior Scientist, Fishing Technology Division 7 Dr. Imelda Joseph Senior Scientist 8 Dr. Prema, D. Senior Scientist 9 Dr. Sobhana, K.S. Senior Scientist 10 Dr. Narayankumar, R. Senior Scientist 11 Dr. Ramachandran, C. Senior Scientist 12 Dr. Shoji Joseph Senior Scientist 13 Dr. Boby Ignatius Senior Scientist Mandapam Regional Centre of CMFRI Mandapam – 623 520, Tamil Nadu Central Institute of Brackishwater Aquaculture No. 75, Santhome High Road, Raja Annamalaipuram Chennai – 600028, Tamil Nadu Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P. O. Kochi – 682 018, Kerala Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P. O. Kochi – 682 018, Kerala Central Institute of Fisheries Technology CIFT Junction, Willington Island Matsyapuri P.O. Kochi - 682 029, Kerala Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P.O. Kochi – 682 018, Kerala Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P.O. Kochi – 682 018, Kerala Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P.O. Kochi – 682 018, Kerala Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P.O. Kochi – 682 018, Kerala Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P.O. Kochi – 682 018, Kerala Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P.O. Kochi – 682 018, Kerala Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P.O. Kochi – 682 018, Kerala 14 Dr. Jayasankar, J. Senior Scientist 15 Dr. Ambasankar, K. Senior Scientist 16 Dr. Kandan, S. Assistant Director 17 Dr. Biswajith Dash Technical Officer 18 Mrs. Shylaja, G. Technical Officer Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P.O. Kochi – 682 018, Kerala Central Institute of Brackishwater Aquaculture No. 75, Santhome High Road Raja Annamalaipuram Chennai – 600028, Tamil Nadu MPEDA, Regional Centre (Aquaculture) 32, Nirmala nagar, Thanjavur – 613 007, Tamil Nadu Visakhapatanam Regional Centre of CMFRI Ocean View Layout, Andhra University P.O. Behind Aqua Sports Complex Visakhapatnam-530 003, Andhra Pradesh Central Marine Fisheries Research Institute Post Box 1603, Ernakulam North P.O. Kochi – 682 018, Kerala CONTENTS Sl. No. 1 Title Faculty Page No. Overview on mariculture and the opportunities and challenges of cage culture in India Dr. Syda Rao, G. 1 History of cage culture, cage culture operations, advantages and disadvantages of cages and current global status of cage farming Dr. Gopakumar, G. 8 Commercialization of Asian seabass, Lates calcarifer, as a candidate species for cage culture in India Dr. Kandan, S. 13 Engineering aspects to be taken care in cage culture of seabass (Cage designs and materials, Mooring materials, Net load calculations etc.) Mrs. Shylaja, G. 17 Netting specifications and maintenance of cages for finfish culture Dr. Saly N. Thomas 23 6 Principles and practices of cage mooring Dr. Boby Ignatius 33 7 Taxonomy, identification and biology of Seabass (Lates calcarifer) Dr. Grace Mathew 38 Nursery rearing of seabass fry and importance of grading and seed transportation Dr. Shoji Joseph 44 9 Important management measures in cage culture Dr. Imelda Joseph 50 10 Integration of seaweed (Kappaphycus alvarezii) and pearl oyster (Pinctada fucata) along with Asian seabass (Lates calcarifer) in open sea floating cage off Andhra Pradesh coast Dr. Biswajith Dash 57 Nutritional requirements of Asian seabass, Lates calcarifer Dr. Ambasankar, K. 60 Feeds and feeding of seabass in hatchery, nursery and grow out system using formulated feeds Dr. Ambasankar, K. 66 Success in hatchery development of seabass and its potential for commercial cage culture in India Dr. Thirunavukkarasu, A. R. 71 Importance of water quality in marine life cage culture Dr. Prema, D. 81 Diseases of seabass in cage culture and control measures Dr. Sobhana, K. S. 87 Open sea cage culture in India A sociological perspective Dr. Ramachandran, C. 94 17 Grow out culture of seabass in cages Dr. Boby Ignatius 99 18 Open sea cage culture: carrying capacity and stocking in the grow out system Dr. Shoji Joseph 102 Growth in fleet size and investment in marine fisheries and scope for open sea mariculture Dr. Sathiadhas, R. 106 2 3 4 5 8 11 12 13 14 15 16 19 20 21 Geographic information systems and site selection issues of open sea cage culture J. Jayasankar 111 Economic analysis of cage culture of sea bass 120 Narayanakumar, R. From 14 - 23 December 2009 Overview on mariculture and the opportunities and challenges of cage culture in India Syda Rao, G. Director, Central Marine Fisheries Research Institute, Post box No. 1603, Ernakulam North P.O. Kochi- 682 018, Kerala, India, gsydarao@gmail.com I ndia is the fourth largest producer of fish in the world expansion of these sectors. With over 8000 km of and the total fish production is around 6 Mt per year coastline there is immense potential for the development and its share in the GDP is around 1.4%. The world annual of mariculture which has taken roots only in recent years. growth rate in aquaculture production has been 7.05% since 1971 (FAO 2008). In 2006, aquaculture comprised 41.8% of total seafood supply. Indian aquaculture has demonstrated a six and half fold growth over the last two decades, with freshwater aquaculture contributing over 95 percent of the total aquaculture production. Given the status of global fisheries, with most large fish stocks being fully exploited or over-exploited, aquaculture production CMFRI has developed several mariculture technologies during last 25 years and concentrated mainly on non finfish like green mussel, edible oyster clams pearl oysters sea cucumbers, several species of ornamental fish, as the scarcity or need for edible marine fish culture was not felt. The demand for cultured marine fish is of recent development in India. must increase in order to maintain or increase the global CMFRI initiated a pearl culture program in 1972 and seafood supply per capita. Fortunately, the aquaculture successfully developed the technology for pearl production sector seems well positioned to succeed in this respect. in Indian pearl oysters. Success in controlled breeding and By obtaining control over the production process and spat production of the Japanese pearl oyster (Pinctada closing the production cycle for an increasing number of fucata ) in 1981 and the blacklip pearl oyster ( P. species, research and innovation similar to what has taken margaritifera ) in 1984 was another important place in agriculture is rapidly improving the breakthrough. CMFRI also took the lead in the development competitiveness of aquaculture, and the blue revolution of the technology required for edible oyster farming during is following the green revolution. the 1970s. Intensive research on various aspects of the India utilises only about 40 percent of the available 2.36 million hectares of ponds and tanks for freshwater aquaculture and 13 percent of a total potential culture of the Indian backwater oyster (Crassostrea madrasensis) has been made and the technology has also been developed for the hatchery production of seed. brackishwater resource of 1.2 million hectares; in other In India, two species of marine mussels namely the green words, there is room for both horizontal and vertical mussel (Perna viridis) and the Indian brown mussel (P. 1 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi indica) are found in rocky coastal areas. Investigation of through large retail chains, where there are risks related the culture possibilities for mussels was initiated in early to retailers’ bargaining power and extensive requirements 1970s by CMFRI which resulted in the development of a to suppliers in terms of deliveries (volume, timing, ), range of practices for the culture of these species. Among documentation, certification, Despite high economic maritime States, Kerala was the first to recognise the risks, the global aquaculture industry continues to attract advantages of utilizing mussel farming technology in rural new production capacity, new entrepreneurs, and new development, from a meagre production in 1997 cultured investors. This is a clear sign of the profitability of the mussel production rose to 1250 tonnes in 2002 with over industry, as high returns are the market’s signal to attract 250 mussel farms being established in the estuaries of more investors and to increase production. There are two Kerala. main explanations for this development. The first is a Considering the substantial contribution aquaculture makes towards socio-economic development in terms of income and employment through the use of unutilised and underutilised resources in several regions of the country, environmentally friendly aquaculture has been accepted as a vehicle for rural development, food and nutritional security for the rural masses. It also has immense potential as a foreign exchange earner. strong underlying growth in the global demand for seafood. This primarily benefits aquaculture as fisheries production cannot grow much above current levels. As an increasing number of the world’s people, particularly in Asia, climb from poverty to the middle class, further growth driven by the demand for variety in protein intake and health concerns is expected. The second is rapid development in the technologies on which aquaculture depend, leading to an almost continuous increase in Aquaculture- a challenging task productivity and quality over time. There is still much room Aquaculture ranks among the most risky businesses to for improvement, e.g. , in genetic material, feed enter as an entrepreneur, farmer, or investor. The risk formulations, disease-control, logistics, distribution, and begins with the production process, as farms face several marketing. With large differences in technological substantial biophysical uncertainties related to disease, sophistication between different species and regions, one water environment, environmental, and climatic can expect productivity development in aquaculture to conditions. For many species a long production cycle from continue to improve the competitiveness of aquaculture fingerlings to harvest contributes to the production risk. species, and with increased demand the production will Market prices for most aquaculture species exhibit be profitable. However, as new technologies are adopted, significant volatility; market access is often restricted by the cyclical and risky nature of the industry will also changing trade regulations; and new competitors continue. continuously enter the market. There are many causes of market risk. Obvious sources are shifts in total supply from Cage culture farmers and consumer demand that is not fully anticipated The cage culture which initiated in Norway during 70s when production decisions are made. When aquaculture got developed into a high tech industry in many countries products are marketed in the international arena, which all over the world for high value fishes. The major is the case for most aquaculture species, producers face advantage in countries where cage culture has been risks related to exchange rate, antidumping, sanitary and commercialised is that they have large, calm and veterinary regulatory changes, and other trade barriers. protected bays to accommodate the cages safely against Finally, aquaculture products are increasingly marketed any unfavourable weather conditions. But in India, such 2 Central Marine Fisheries Research Institute From 14 - 23 December 2009 areas are very few and the sea conditions are system made of butt-welded HDPE pipes, designed for unpredictable during monsoon seasons leaving the safety the culture of fishes such as milkfish, mullet, cobia or of structures uncertain. Also, the Government of India or pompano seabass, koth, ghol lobsters are used in many any maritime States have no policies regarding commercial countries. mariculture and leave alone open sea cage farming. Many countries try to venture into Indian arena to sell aquaculture equipments including cage related products which are suitable for their environment and may not be to Indian conditions. But, all are reluctant to transfer technologies suitable to Indian conditions and foreign consultants charge exorbitantly for consultancy. Fish farming in cages is a lucrative business for otherwise poor coastal communities and it is an industry that is growing rapidly in many Asian countries. In some countries and locations, cage farming provides an important source of fish production and income for farmers, other industry stakeholders and investors. Of the estimated one million tonnes of marine fish cultured in Asia, probably 80-90 % is from cage farming. Most of the research relates to cage aquaculture in temperate waters, an industry that has been well established for more than 30 years, particularly for salmon. In modern times, cage culture is also seen as an alternate livelihood, for example, for persons displaced by the construction of reservoirs or acquisition of land for other developmental activities. In such a situation, cage aquaculture has emerged as a promising venture and offers the farmer a chance for optimal utilization of the existing water resources which in most cases have only limited use for other purposes. By integrating the cage culture system into the marine aquatic ecosystem, the carrying capacity per unit area is optimized because the free flow of current brings in instantaneous exchange of water and removes metabolic waste and excess feed. Thus economically speaking, cage culture is a low impact farming practice with high economic returns and with least carbon emission activity. In view of the high production attainable in cage culture system and the presence of large sheltered coastal waters in many countries, marine cage farming can play a significant role in increasing fish production. Success of open sea cage farming in India For the first time in India a marine cage was successfully launched at Visakhapatnam, in the east coast of India by CMFRI in 2007. The indigenously designed and fabricated HDPE cage was provided with a cat walk for free working on board and stabilization. The cage net was 15 m diameter and 6 m deep. An outer HDPE predator net protected the cage net from damage by large predators. On top of the cage railing, a bird net was provided to prevent bird attacks. The entire structure was kept in position by ballast and ropes tied to the mooring chains. The cage was provided with a shock absorber on the mooring chain to withstand and absorb the pressure of winds, currents Cage is an aquaculture production system made of a and was moored at a depth of 11 m about 300 m from the floating frame, net materials and mooring system (with shore line. The total net volume was 850 cubic meters. synthetic mooring rope, buoy, and anchor) as a round or This area being under the influence of high water currents, square shape floating net pen to hold and culture large strong waves, and winds and generally rough, the cage number of fishes and can be installed in reservoir, river, was intact. Limited number of Asian seabass, Lates lake or sea. The design of the cage and its accessories calcarifer, was stocked during the first trial and successful can be tailor-made in accordance to the individual farmer’s harvesting was carried out after four months during the requirements. HDPE float frames installed in open trawl ban period in the east coast. The economic analyses unprotected water can withstand wave conditions. Round of the operation have revealed the viability of cage culture cage (volume depends on diameter) with floatation in Indian waters. Other successful models are lobster 3 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi (Panulirus homarus) at Trivandrum, Kerala and seabass at if adequate post harvest measures are adopted for live Balasore, Orissa. At Balasore, culture of seabass in cage fish export to countries where such fish fetch good market was undertaken during 2009 and despite of several odds, price. At present only shellfish is leading Indian export a catch of 3.1 t was harvested with the active cooperation and the scenario can be changed if we can assure post of fishermen. production quality for harvested marine fishes. Opportunities for cage culture in India An educated workforce and people with excellent animal General husbandry skills: sufficient number of fisheries graduates and specialists in different areas of fish farming (Nutrition, The Indian sub continent presents open sea aquaculture pathology, environment ) are available in India to make producers with a number of opportunities: the cage farming sector technically fool proof. A huge area to convert to mariculture farm: The Indian Local availability of trash fish: There are 3827 fishing coastline is extending up to 8129 kilometres and has a villages and 1914 traditional fish landing centers in India continental shelf area of 5.3 lakh km2. With numerous and if proper effort is put in preserving the trash fish, they creeks and saline water areas the opportunities for cage can be utilised for feed, feed ingredient for compounded culture are tremendous in India. feed. Availability of local feed manufacturers and suppliers Well experienced fishermen work force: India has a huge also are added advantage. human resource of about 14.66 million fishermen Strong research and extension capabilities: In India there population including adult fishermen (8.7 million), full time are 8 National Fisheries Research Institutes, equipped (0.93 million), part time (1.07 million),and those who are with well experienced researchers and infrastructure involved in ancillary activities like net making, processing facilities. CMFRI and CIBA are doing extensive research and fish vending (3.96 million). Development of in marine and brackishwater aquaculture and since CMFRI mariculture through cage farming can be taken up with a has pioneered in open sea cage farming, it will be an added focus on sustainability through empowering the fishermen strength for entrepreneurs to have consultants within the by achieving employment generation, social security and country rather than spending on foreign experts. There increased food security and augmenting sea food exports. are extension researchers as well as officers in different Many of these wild fish harvesters represent a highly national and state level organisations and it is also helpful trained workforce that have extensive knowledge of the when new and novel technologies are introduced to ocean, boat handling, net mending and maintenance, fish aquaculture sector. harvesting and quality control that aquaculture companies can easily adapt to their own operations. In these cases, previous wild fish harvesters would require only some basic training associated with standard farm operations and fish health management. Strong domestic and export markets : It is a major Marine cage culture also presents an excellent opportunity to maintain coastal communities that are presently reliant upon over-harvested commercial fisheries (In the simplest terms one 6 m diameter cage is equivalent to one ha pond on land with regard to production and with less work). advantage of Indian sub-continent that it has an excellent domestic market for fish and if supply is assured during Challenges or constraints fishing ban seasons, the returns to the farmer will be very Lack of clear regulations for use of open sea waters: The attractive. Similarly export also can be enhanced for fish Indian seas are open to all Indians and the lack of any 4 Central Marine Fisheries Research Institute From 14 - 23 December 2009 policy in utilisation of open waters has to be tackled in a z Site should be at least 6- 8m (depending on the net positive manner. By allocating areas for cage farming, by depth) deep over a sizable area, with sandy or rocky means amicable to fishermen and other users of the sea bottom (navigation, tourism ) this can be overcome. z Competition arises from other uses of coastal and offshore waters such as recreational boating, commercial fishing and shipping Rising costs of inputs such as energy and feed: Demand located away from sources of pollution z Wind and wave action should be at moderate levels z Site should not be a regular fishing ground or a navigation channel so that interference would be and supply are not matching in many cases and therefore hindrance for the operation cost escalation in aquaculture operations also inevitable. Concerns by fishermen about competition from aquaculture: due to lack of awareness and insecure z Site should have an all weather access z Nearest beach should have required low valued fish source to be used as feed feeling, fishermen resist on any venture in the sea. Only solution is to get them involved in cage culture operations z also. By experience in the field they will also change their z Before starting any new venture, it is of no concern about environment or sustainability. But over the years, that becomes the major concern. So before initiating cage culture, it is better to plan out a scheme for environmental concern over the years which will help in flourishing aquaculture rather than killing it. There should be adequate availability of labour and materials mind set. Concerns about environmental effects of aquaculture: Site must have good water quality and should be Cages should be easily monitorable Cage models Another challenge to tackle over is in selection of cage models and the design of the cage is directly related to the chosen site, inshore or offshore. According to the analysis of Loverich and Gace (1997) on the effect of currents and waves on several classes of cages for Technological challenges: Since the industry is new to offshore, the most suitable cage is a self-supporting cage. India, many stake holders will come with many offers, However, for inshore or sheltered sites the conditions but no proven technology is available so far. change and gravity cages can be used. Some countries Other challenges Site selection tend to move the cages offshore due to legal and possible pollution problems, but the open sea cages face other problem like rough sea. In all the cases, whether inshore, Site selection is the biggest challenge in determining offshore, or sheltered, the cage structures must withstand commercial viability of cage culture. Identifying a location the forces of the currents, waves and winds, while holding that has the optimum water quality (temperature, oxygen, the stock securely. There are a number of types of cages. light and nutrient levels), current movements and other Beveridge (1996) proposed four basic types: a) fixed; b) infrastructure facilities is the most critical factor in cage floating; c) submersible; d) submerged. culture. Various cage types and systems are being used for finfish Criteria to be considered before selecting a site for cage farms all over the world, the choice of which is usually culture are: determined by the following main factors: 5 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Site: The most important aspect to be considered is the establishment of broodstock and hatchery facilities and site in which the cages will be set up and their suitability also to the complicated larviculture procedures involving with regard to (i) exposure to potential sea storms, (ii) culture of proper live feeds, their nutritional enrichment, seabed characteristics and depth, (iii) prevailing sea feeding protocols, grading, water quality maintenance, conditions, and (iv) visual impact. An exposed site and an nursery rearing and disease management. The production increased risk of heavy storms will require cages, nets of seed of the concerned species by development of and mooring systems designed to resist the maximum commercially viable technologies is essential for registered storm strength. If the site is somewhat development of sustainable mariculture practices, but sheltered, a simplified mooring system and lighter rearing many of these technologies are still in the emerging state structure will reduce the cost of the initial investment. and may take several years for standardisation on a cost Should negative interactions be encountered with coastal effective level. High value species like Asian sea bass for tourism; submerged or low visual impact models are often which hatchery seed as well as natural fingerlings available considered and/or possibly recommended by the at different locations in India is ideal to be stocked in authorities responsible for the issuance of the farming cages. More hatcheries are to be set up for seabass along license. the Indian coast for continuous supply of seed. Cost of cages: The initial cost of the investment usually Capture based aquaculture (CBA) is an alternative for those represents a limiting factor particularly for those investors species for which hatchery technology is not developed. with a fixed budget. However, the cheapest option may As hatchery technologies remain to be perfected for many not take into consideration the suitability of the structures species, fish farmers have to depend on ‘seed’ available for the site. from the wild. CBA has developed due to the market Production plans: The size of the farm and cage model may vary depending on the target pursued by the investors. For instance, farmers aiming to produce a niche product, or attempting to diversify production with fish of various sizes, may prefer a large number of small cages rather than a few large ones so that only a reduced percentage of volume can be engaged in a selected production. demand for some high value species whose life cycles cannot currently be closed on a commercial scale. CBA is a world-wide aquaculture practice and has specific and peculiar characteristics for culture, depending on areas and species. The species/ groups that can be harvested as wild juveniles include shrimps, milkfish, seabass, mullets, pomfrets, groupers, red snappers, koth, lobsters It is generally considered that further development of marine aquaculture is possible only by the increase in mass Species selection and seed availability production of juveniles in hatcheries. But it remains a fact It is well known that availability of seed in adequate that much of world’s coastal aquaculture can still be quantities is one of the major challenges in the expected to come only from the supply and availability of development and expansion of mariculture. Though seed capture-based juveniles. The species include seer fish, production technologies have been developed for many pomfrets, mackerel, koth, shrimps Also, there exists a good marine finfish and shellfish species, many of these fishery for live juveniles of different species of lobsters technologies have not been scaled up to commercially but very little are used for fattening. It is estimated viable levels. The hatchery seed production of many high conservatively that about one million of seer fish juveniles value marine finfishes and shellfishes is complex and of 7-10 cm and two millions of mackerel juveniles of 5-8 expensive due to the high costs involved in the cm land by shore seines in the month of April alone along 6 Central Marine Fisheries Research Institute From 14 - 23 December 2009 the stretch of Visakhapatanam- Kalingapatnam. If only a cages. As on today there is no indigenous scientifically small fraction of these seed/juveniles are induced to be developed marine finfish feed. The development of feed brought in live condition, they form very good source of is also very complicated and need to look into nutritional CBA without affecting the ecosystem and livelihood of balance for carnivorous fish, feed conversion and cost fishermen. It will be more lucrative for the fishermen at effectiveness. The imported feeds for seabass are sold at the same time contributing to several fold increase in the Rs 80/kg which is not economical for most of the farming mariculture production. Juvenile yellow fin tuna are operations. available in plenty in and around Lakshadweep waters which can be used for farming in cages. Feed Conclusion With all the challenges to be faced, it is felt that with innovations in cage culture as suitable to Indian conditions Availability of cost effective and nutritionally balanced can result in opening up a new horizon in Indian fisheries, feed is another constraint for high value fish culture in especially in mariculture. 7 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi History of cage culture, cage culture operations, advantages and disadvantages of cages and current global status of cage farming Gopakumar, G. Mandapam Regional Centre of Central Marine Fisheries Research Institute Mandapam Camp, Tamil Nadu - 623 520 drggopakumar@gmail.com Introduction The earliest record of cage culture practices dates back to the late 1800 in Southeast Asia, particularly in the freshwater lakes and river systems of Kampuchea. Marine fish farming in cages traces its beginning to the 1950s in Japan where fish farming research at the Fisheries Laboratory of the Kinki University led to the In Europe, cage culture of rainbow trout (Oncorhynchus mykiss) in freshwater began in the late 1950s and in Norway, Atlantic salmon (Salmo salar) followed in the 1960s. More than 40% of its rainbow trout comes from freshwater cages. Salmonid culture is currently dominated by production from Norway, Scotland and Chile. Cage culture of fish was adopted in USA in 1964. commercial culture of yellow tail Seriola quinqueradiata Currently many fish species have been cultivated in and developed into a significant industry as early as various designs and sizes of cages in Asia, Europe and 1960. Since the 1970, Thailand has developed cage other parts of the world. Tilapia and carp predominate in culture techniques for two important marine finfish: the freshwater cage culture in Asia, while salmonids are sea bream (Pagrus major) and grouper (Epinephelus spp.). commonly farmed in Europe and the Americas. Large scale cage farming of groupers were established The rapid growth of the industry in most countries may be in Malaysia in 1980. Korea started cage culture in the attributed to the availability of suitable offshore sites for late 1970s and by the end of 1980, cage culture of the cage culture, well established breeding techniques that yield olive flounder (Paralichthys olivacens) and black rockfish a sufficient quantity of various marine and freshwater fish (Sebastes schlegeli) was established, and developed into juveniles, availability of supporting industries such as feed, a successful aquaculture industry in the 1990s. Cage net manufactures, fish processors etc., strong research and culture of groupers (Epinephelus spp.) in the Philippines development initiatives from institutions, governments and has been practiced since 1980s. Mariculture of milkfish universities and the private sector ensuring refinement and in the 1990s led to the further growth and development improvement of techniques/ culture systems, thereby of the industry. further development of the industry. 8 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Cage culture operations Advantages Cage culture operation involves: z artisanal type or modern sophisticated ones. Stocking: The stocking density of fish depends on the carrying capacity of the cages and feeding habits of the z z z community (fishermen) whose income is affected by Feeding: Many biological, climatic, environmental and many reasons in fishing sector. It therefore acts as an economic factors affect feeding of fish in the cages. time. Each species varies in maximum food intake, feeding frequency, digestibility and conversion efficiency. These in turn affect the net yield, survival rates, size of fish and overall production form the cage. Trash fish is the main feed for yellowtail, grouper, bream, snapper and other Cages make use of existing water bodies and thus it can be given to non-land owned people of the optimum yield and low disease prevalence. Growth rate is affected by feeding intensity and feeding Cage reared fish are superior in quality in terms of condition factor, appearance and taste secondary productivity of the sites. The optimal stocking density varies with species and size of fish and ensures Observation of the stock is easy in cages, therefore feeding and routine management is easy cultured species. For those species which are low in the food chain, stocking will also depend on the primary and Construction of cage is comparatively easy, be it alternative income for such groups. z Harvesting is typically less labour intensive in cages z Fish are protected from predators and competitors Disadvantages z Pond fish can make use of naturally occurring food, while cage grown fish only have a limited access carnivorous fish species cultured in marine cages. The natural food since they cannot forage on their own. shortage of trash fish is a major problem in many countries Cage grown fish therefore needs to be fed by the with large scale cage farming. farmer to a much higher extent. The food that is given Farm management: Farm management must optimize to the cage grown fish also has to be nutritionally production at minimum cost. Efficient management complete, e.g. contain proper amounts of all necessary depends heavily on the competence and efficiency of the vitamins and minerals. farm operator with regard to feeding, stocking, minimizing loss due to diseases and predators, monitoring z When fish grown in cages instead of ponds, most farmers opt for a high stocking density. A high stocking environmental parameters and maintaining efficiency in density creates a stressful environment for the fish technical facilities. Maintenance works are also very vital and stress damages the immune system. The risk of in cage culture. disease is therefore high. The risks will be increased Advantages and disadvantages of cages compared to further if the farmer fails to provide the fish with land based structures optimal water conditions and a satisfactory diet. Cage culture can introduce or disrupt disease and parasite The advantages and disadvantages of cage culture is cycles, change the aquatic flora and fauna and alter adjudged by its comparative performance with other land the behaviour and distribution of local fauna. based culture systems in terms of level of technology required for construction, ease of management, z If proper water exchange is not there, the uneaten adaptability, quality of the fish reared, resource use, social feed and metabolic waste released from cages will implications, and economic performance. lead to eutrophication of the site. 9 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi z z Predators can be attracted to the cages and for that population growth, increasing affluence and urbanization additional protection has to be provided such as in developing countries are leading to major changes in predator nets supply and demand for animal protein from both livestock Poaching is easy because fish are confined in a small area and fish. The move within aquaculture toward the development and use of intensive cage farming systems was driven by z Marine cages face problems like fouling and is more a combination of factors, including the increasing expensive competition faced by the sector for available resources, the need for economies of scale and the drive for increased z Storms can damage the cages. z When cages are installed indiscriminately, its impact suitable sites resulted in the sector accessing and on environment and biodiversity is adverse and it will expanding into new untapped open water culture areas have influence on current flow and increase local such as lakes, reservoirs, rivers and coastal brackish and sedimentation marine offshore waters. Since cages occupy open water sources, it may affect Production navigation in the area, or reduce landscape value of Total reported cage aquaculture production from 62 that area and are vulnerable to pollution from any countries and provinces/regions from where data is source. available amounted to 2412167 tonnes (excluding China) z Current global status of sea cage farming productivity per unit area. Particularly the need for On the basis of the reported information, the major cage culture producers in 2005 included - Norway (652306 Although no official statistical information exists tonnes), Chile (588 060 tonnes), Japan (272 821 tonnes), concerning the total global production of farmed aquatic United Kingdom (135 253 tonnes), Vietnam (126 000 species within cage culture systems or concerning the tonnes), Greece (76 577 tonnes), Turkey (78 924 tonnes), overall growth of the sector, there is some information and the Philippines (66 249 tonnes). on the number of cage rearing units and production statistics being reported to FAO by some member Major cultured species, cage culture systems and countries. In total, 62 countries provided data on cage culture environments aquaculture for the year 2005. To date commercial cage culture has been mainly The cage aquaculture sector has grown very rapidly during restricted to the culture of higher value ( in marketing the past 20 years and is presently undergoing rapid terms) compound-feed-fed finfish species, including changes in response to pressures from globalization and salmon (Atlantic salmon, coho salmon and Chinook growing demand for aquatic products. Fish consumption salmon), most major marine and freshwater carnivorous in developing countries will increase by 57 percent from fish species (including Japanese amberjack, red sea bream, 62.7 million metric tons in 1997 to 98.6 million in 2020. yellow croaker, European seabass, gilthead sea bream, By comparison, fish consumption in developed countries cobia, sea raised rainbow trout, Mandarin fish, snakehead) will increase by only about 4 percent, from 28.1 million and an ever increasing proportion of omnivorous metric tons in 1997 to 29.2 million in 2020. Rapid freshwater fish species (including Chinese carps, tilapia, 10 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Colossoma and catfish). However, cage culture systems employed by farmers are currently as diverse as the number of species currently being raised, varying from traditional family –owned and operated cage farming operations (typical of most Asian countries; to commercial cages used in Europe and the America). Table 1 Production of the top ten marine and brackish water cage aquaculture countries Country Quantity (Tonnes) Norway 652 306 in percent of total 27.5 Chile 588 060 24.8 China 287 301 12.1 Japan 268 921 11.3 United Kingdom 131 481 5.5 In terms of diversity, altogether an estimated 40 Canada 98 441 4.2 families of fish are cultured in cages, but only five Greece 76 212 3.2 families (Salmonidae, Sparidae, Carangidae, Pangasiidae Turkey 68 173 2.9 and Cichlidae) make up 90 percent of the total Republic of Korea 31 192 1.3 production ad one family (Salmonidae is responsible for 66 percent of the total production. At the species Table 2 Production (tonnes) of the top ten species / taxa in marine and brackish water cage aquaculture (excluding PR China) level, there are around 80 species presently cultured in cages. Of those, one species (Salmo salar) accounts for about half (51 percent) of all cage culture production and another four species (Oncorhynchus mykiss, Seriola quinqueradiata, Pangasius spp and Onchorhynchus kisutch) account for about another one fourth (27 percent). Ninety percent of total production is from only eight species (in addition to the ones mentioned above: Oreochromis niloticus, Sparus aurata, Pagrus auratus and Dicentrarchus labrax ) the remaining 10 percent are from the other 70+ species. Species Quantity (tonnes) Salmo salar Oncorhynchus mykiss Seriola quinqueradiata Oncorhynchus kisutch Sparus aurata Pagrus aurata Dicentrarchus labrax Dicentrarchus spp Oncorhynchus tshawytscha Scorpaenidae in percent of total 219 362 58.9 195 035 9.4 159 798 7.4 116 737 5.6 85 043 4.1 82 083 4.0 44 282 2.1 37 290 1.8 23 747 1.2 21 297 1.0 On the basis of the information gathered from the regional Integrated cage farming reviews, Atlantic salmon is currently the most widely Cage culture systems need to evolve further, either by cage-reared fish species by volume and value; reported going further offshore into deeper waters and more aquaculture production of this coldwater fish species extreme operating conditions and by so doing minimizing increased over 4000-fold from only 294 tonnes in 1970 environmental impacts through greater dilution and to 12 35 972 tonnes in 2005 (Valued at US$4 767 000 possible visual pollution or through integration with lower- million), with significant production of more than 10 000 trophic-level species such as seaweeds, molluscs and tonnes currently being restricted to a handful of countries, other benthic invertebrates. including Norway, Chile, the United Kingdom, Canada, and the Faroe Islands. The rationale behind the co-culture of lower-trophic- level species is that the waste outputs of one or more species Most of the top marine and brackish cage aquaculture groups (such a cage reared finfish) can be utilized as inputs producers are found in temperate regions (Table 1), while by one or more other species groups, including seaweeds, the top species include salmonids, yellowtails, perch-like filter feeding molluscs and /or benthic invertebrates such fishes and rockfishes (Table 2). as sea cucumbers, annelids or echinoderms. However, 11 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi while there has been some research undertaken using land already much pressured coastal environments, there is based systems considerably, further research is required increasing agreement that particular emphasis has to be on open or offshore mariculture systems. given to the environmental sustainability of the subsector. Cage aquaculture will play an important role in Prospects the overall process of providing enough (and acceptable) Cage culture has great development potential. For fish for all, particularly because of the opportunities for example, intermediate family-scale cage culture is highly the integration of species and production systems in near- successful in many parts of Asia and one of the key issues shore areas as well as the possibilities for expansion with for its continued growth and further development will installation of cages far from the coast. not be how to promote but rather how to manage it. Even though the sea cage farming has been advancing in However, there is also an urgent need to reduce the many Asia-Pacific countries such as China, Indonesia, current dependence of some forms of cage culture Japan, Philippines, Taiwan, Vietnam and Korea in recent systems in Asia upon the use of low value/ trash fish feed years, it still remains to be commercialised in India. The inputs, including those for Pangasid catfish and high value Central Marine Fisheries Research Institute has been species such as Mandarine fish, snakehead, crabs and taking pioneering and massive steps towards this direction marine finfish. currently. The major constraint for popularization of cage farming in India is the less availability of sheltered areas However, the intensive cage culture of high value finfish which are ideally suited for sea cage farming. In this is growing fastest and there are important social and context, the development of advanced types of mooring, environmental consequences of this growth and anchor and floating systems which can withstand the transformation of the sub-sector. Similar to global tends impact of adverse weather and currents will help us to in livestock production, there is a risk that the fast growth venture into more unsheltered open sea areas. Hence, it of intensive operations can marginalize small-scale is felt that more technological and engineering producers and high production at different levels of interventions in cage farming coupled with large-scale intensity can lead to environmental degradation if not hatchery production of high value and fast growing properly planned and managed. Considering that most finfishes can pave the way for the development of sea of the cage aquaculture takes place in the fragile yet cage farming industry in our country in near future. 12 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Commercialization of Asian seabass, Lates calcarifer as a candidate species for cage culture in India Kandan, S. Marine Products Export Development Authority, Regional Centre (Aqua), Thanjavur shanmugakandan@yahoo.co.in Introduction Asian Seabass (Lates calcarifer) a popular edible marine Besides, advances have been taken place in addressing health management challenges encountered while farming. finfish commands consistent demand in domestic and In India, seabass has been cultured in brackishwater and international markets. It is widely distributed in Indo- freshwater by stocking wild seed in some part of West Pacific region and extending up to Taiwan, South East Bengal, Tamil Nadu and Kerala. The cage culture of Australian coast, Papua New Guinea, Arabian Sea and Bay seabass is still in its developmental stages, even though of Bengal and further to Persian Gulf region. In India, the culture of seabass in different types of cages is now seabass fishery is reported from all along the coast established by MPEDA (in ponds), RGCA (in ponds) and including Andaman & Nicobar Islands. Due to the CMFRI (open waters). For the past five years, considerable characteristic catadromous pattern of life cycle, its development has been made in culture of the species in population occupies a wide range of habitats starting from cages in ponds of all bio categories and hi-tech cages in freshwater lakes, rivers, estuaries and inshore coastal open sea. But, many problems are remaining unsolved. waters. However, the adult fish migrate to deeper inshore Some problems encountered are: sea areas for spawning and as such the early cycle is restricted in seawater areas. Besides, exploiting its natural resources from different environmental conditions, seabass become a compatible species for aquaculture in i) from 1.0-1.5 cm. to 6- 7 cm fingerlings ii) iii) Non-availability of extruded pellet feed for growout Status of seabass culture in India cultured in South East Asian Countries, China and Australia. Lack of availability weaning diet required for nursery rearing saline water as well as freshwater conditions. Asian Seabass in one of the prominent species being Cannibalism during fingerling production from fry iv) Non availability of proper culture techniques in different bio categories. Several commercial hatcheries produce seeds for Despite of all the above problems, the culture of seabass aquaculture purpose in these countries and also evolved in cages in the pond or in the open water is being initiated suitable feed for growing seabass in aquaculture systems. and standardized according to the Indian conditions. 13 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Culture technology for growing fish in cages in pond cages can be fixed in PVC frames of floating frame, sinker Seabass can be cultured in freshwater or brackishwater and top lid. Around 2000 – 3000 fry can be stocked and ponds; but cannibalism is one of the most serious monitoring of the fries is easy in net cages. Also, the problems in seabass culture. In order to minimize the maintenance cost of the net cages is lesser than the chances of cannibalism, culture is carried out in two hapas. The only constraint is that, a floating feed should phases, i.e. the nursery phase and grow-out phase. be used in cages for rearing seabass. The mesh size of the cage is 2 mm, 4 mm, 6 mm and 8 mm. The fry will grow faster in net cages than hapas as it facilitates more Nursery phase The main purpose of the nursery is to culture the fry from hatchery (1.5 – 2.5 cm) to juvenile size (6-7 cm). The aerations and water circulation movements inside the cages. nursery rearing can be carried out either in earthen ponds Food and feeding or hapas. Nursery pond size ranges from 1000 to During the nursery phase extruded slow sinking feed is 2000 m2 with a water depth of 80 – 100 cm. Pond with preferred. Crumbled feed should be provided according separate inlet and an outlet gate to facilitate water to the requirements and subsequently the pellet size can exchange is recommended. Pond bottom should be flat be increased. The size of the pellet during the nursery and sloping towards the drainage gate. Inlet and outlet phase is highly correlated with the mouth size of the gates are provided with a fine screen (1 mm mesh size) to seabass fry (Table 1). Table 1. Size of the fish and size of the feed Size of the Fish(g) Length(cm) Size of feed(mm) Type of feed 0.05 – 0.08 1.5 – 2.0 0.3 mm (Dust) Slow sinking 0.08 – 0.40 2.1 – 3.0 0.5mm (Crumble) Slow sinking 0.50 – 0.80 3.1 – 4.0 0.8mm (Crumble) Slow sinking 0.90 – 1.65 4.1 – 5.0 1.0mm (Starter-1) Slow sinking Slow sinking 1.70 – 2.60 5.1 – 6.0 1.2mm (Starter-2) 2.70 – 4.00 6.1 – 7.0 1.5mm (Starter-3) Slow sinking 5.00 – 7.00 7.1 – 8.0 1.5mm (Starter-3) Slow sinking prevent predators and competitors from entering and the The nursery period lasts for about 32 – 45 days until it fry from escaping the pond. Fry ranging from 1.5 – 2.5 cm reaches the fingerlings size (5 – 7 cm). During this period, are suitable for stocking in nursery ponds. Stocking water exchange should be done according to the density is between 20 – 50 individuals per cubic meter. requirements and water quality conditions. It is to be However, it is advantageous to conduct nursery rearing monitored that the minimum feed wastage is occurred of seabass in hapas because it enables closer monitoring so as to get profitable nursery rearing of seabass. and grading resulting in uniform size stocking and better survival compared to open-pond rearing. It is likewise easy to maintain and require very little capital investment. Grading The mechanical grader available in the market can be used for grading the fries. Initially, once in three days and later Nursery rearing in cages weekly once the grading has to be done to separate the The seabass fry can be grown to fingerlings in net cages shooters and the bigger seabass fry. This exercise will measuring 1 M x 1 M x 1 M, made up of HDPE. These net give more survival rate with better growth as the seabass 14 Central Marine Fisheries Research Institute From 14 - 23 December 2009 fries are getting the suitable feed according to their mouth Seabass cages usually are made of Nylon or Polyethylene size. Also, the cannibalistic characteristics drastically or HDPE Netting with varying mesh size depending on come down due to timely grading. the size of the fish grown. At the stage, the fingerlings are ready for transfer to growout system and this can be harvested from the hapas by scooping and transfer to grow-out ponds after proper Table 2 Different cage mesh sizes and size of the fish to be stocked Total Length of Fish (cm) Cage Mesh Size (mm) 7-9 counting so as to calculate the daily feeding regime. 8 9 - 11 12 11 - 15 16 15 - 18 20 grown to more than 7 - 10 cm or more than 10 – 15 g is 18 - 22 24 ideal. 22 - 26 32 26 - 32 38 32 and above 44 For open sea cage culture, the seabass fingerlings Grow-out phase The most common grow-out system is pond culture, in The stocking densities in the cages vary according to the either brackish or freshwater. A pond having minimum size of the fish, as the culture progresses and the fish water depth of 6 – 8 feet is required for cage culture. grow in size the density has to be adjusted suitably. The Fish are usually maintained in cages within the pond, suggested stocking densities are given below: although cage culture of fish less than 120 – 150 mm TL Table 3 Suggested stocking density in cages based on number/ m3 and free-ranging of larger fish are sometimes combined (Schipp, 1996). Size (cm) Stocking density no./Cu.M. With aeration Without aeration The cages are usually 4 – 5 m2 (water surface area) and 2 7.0 – 9.0 600 350 – 4 m deep. They may hold 15 – 40 kg/m3, provided they 9.0 – 12.0 500 250 12.0 – 15.0 400 200 will stress the fish. Typically, the pond is aerated and 15.0 – 20.0 300 180 20.0 – 24.0 200 140 receives water exchange of 5 – 10 per cent of pond volume 24.0 – 28.0 150 100 per day, if necessary. 28.0 – 30.0 100 70 30.0 – 32.0 50 30 32.0 – 34.0 30 15 are cleaned off bio-fouling regularly, as poor water flow In India, a technology has been developed and perfected for culturing of seabass in cages in pond by RGCA, an R&D, the arm of the Marine Products Export Development Feed Authority. In this method, the pond cages having the At present, seabass culture is facing the non-availability dimension of 2 M x 2 M x 1.3 M (approx. 5.0 Cu.M.) using of floating extruded pellet feed which is the major PVC pipe frames of 40 mm (floating frame), 32 mm constraint. However, few companies in India have come (sinker), 25 mm (top lid). The cages are fastened to the forward to manufacture feed for seabass culture, which bamboo or wooden poles of the catwalks fixed in the is highly suitable for cage culture. Even though, trash ponds. The catwalks are provided for the purpose of day- fish are given widely for the culture at present in many to-day management activities, such as feeding, sampling, places for sustainable aquaculture, the pellet feed is the grading etc. highly recommended. The feed should be given twice 15 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi daily in the morning hours, 6 – 7 A.M. and evening 6 – 7 If fish is weighing an average 1 kg weight, around 100 P.M. at the rate of 8 – 10% total biomass in the first 2 nos. of fish can be stocked in the 5 m3 area. The harvest months of culture. After 2 months, feeding is reduced to of the fish grown in the cage can be done with minimum once daily and given during late evening at the rate of 2 labors and effort. Around 10 tons production can be – 5% of the total biomass. The floating pellet feed should harvested within 3 – 5 hours from 100 cages. As the fish be given only when the fish swim near the surface to eat. are grown in the cages is giving good muscle structure, The suggested feeding schedule for extruded pellet feed taste and flavor, it is always fetching an average rate of is given below: Rs.150 – 180 in India (the price vary according to the Table 4 Suggested feeding schedule, as % of body wt., type of feed, etc. Size (cm) Feed as % of body weight Pellet Size (mm) Type of feed 7-9 10 - 12 13 - 15 15 - 18 18 - 20 20 - 22 22 - 25 25 - 27 27 - 30 8.0 7.0 6.0 5.0 4.0 3.5 3.0 2.6 2.2 2 2 3 5 5 7 7 9 9 Slow sinking Slow sinking Slow sinking Floating Floating Floating Floating Floating Floating 30 - 35 2.0 11 Floating FCR local demand) and in export, fetching US$ 4 – 5 per kg. Note: For open sea cage culture, the mesh size of the cage is same and only the width of the cage (circular or rectangular) will vary according to the stocking density and environmental conditions prevailing in the open sea. The frame for open sea cage culture, HDPE material is recommended. Stocking density, feed and feeding type and all other aspects are almost similar to the culture of seabass in cages in the pond. Conclusion In India, the aquaculture is centric to the shrimp/scampi production and these two species are contributing in total of 52% towards export. The freshwater fish produced through aquaculture is mainly catering to the domestic market only. In Indian seawater many finfish and shell For any aquaculture practice, the FCR is the determining fishes are abundant for aquaculture, which is economically factor for the economic viability of the fish culture for important, the seabass (Lates calcarifer) fish is occupying domestic or export and also the cost of production per the main role at present as it is a candidate species for unit. For seabass, 1: 1.2 FCR is recommended by using cage culture as it has completed a value chain approach extruded pellet feed and 1: 5 – 7 is the observed FCR by from seed production, nursery rearing, grow-out and using trash fish or farm made feed. marketing & export by MPEDA through its R&D Institute Production, harvest & marketing In a 2 M x 2 M x 1.3 M cage, around 80 – 100 nos. is the recommended stocking density (biomass) in pond system. – RGCA. Note: The above text and results presented here are based on the various demonstrations conducted on culture of seabass in cages in ponds by MPEDA-RGCA. 16 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Engineering aspects to be taken care in cage culture of seabass (Cage designs and materials, Mooring materials, Net load calculations etc.) Shylaja, G. Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India shylusuresh@rediffmail.com Aquaculture systems are very diverse in their design and mechanical wear and corrosion. Repairs and salvages are function. The three most basic categories of culture more difficult and in some cases access may be denied to systems are: i) Open systems, ii) Semi closed and iii) some structures during a storm. Because of all these Closed systems. reasons the design of an aquaculture cage system is very Modern cage culture began in 1950’s with the advent of synthetic materials for cage construction. The major advantage of cage culture is use of existing water bodies, technical simplicity, simplified harvest and low capital cost compared with land based farm. But it has got certain complex in nature and of course the most difficult task. Hence, it is essential to select a proper site, ideal construction materials and proper designing, suitable mooring and good management etc in bringing out a cage culture production more profitable and economical. disadvantages like feed must be nutritionally balanced, Four different types of cages are fixed, floating, pollution, out break of disease, vandalism etc. submersible and submerged (Fig. 1) Engineering considerations in the design of cages The sea is perhaps the most difficult environment for Engineering. The sea can generate great storm forces on any floating or sea bed mounted structure and storm events occur randomly. The constant 24 hour per day bending compression and tension within structural member are optimum conditions for fatigue. Similarly constant motion in a corrosive fluid is ideal for Fig. 1 Characteristics of different types of cages 17 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Fixed cage consists of a net supported by posts driven into the bottom of a lake or river, they are completely inexpensive and simple to build, but their use is restricted to sheltered shallow sites with suitable substrates. The floating cages have a buoyant frame or collar that support the bag, they are less limited than most other cages in terms of site requirements and can be made in a great variety of designs ,and are the most widely used ones. The submersible cages rely on a frame or rigging to maintain shape. The advantage over other designs is that its position in the water column can be changed to take advantage of prevailing environmental conditions. Generally these cages are kept at the surface during calm weather and submerged during adverse weather. The submerged cages can be wooden boxes with gaps between the slots to facilitate water flow and are anchored to the substrate by posts or stones. The major components of a cage farm are a) cage bag, b) floats, c) frame, d) service system, e) mooring system and f) anchor system. The cage frame, nets used for cages and the mooring system has to withstand all types of weather conditions all year round. Net failure is an important source of fish loss in cage culture systems. So while making a net for a specific purpose many considerations are taken into account such as the forces applying on the net, the kind of materials the net and rope frame made from and the way in which they are tied. The main forces on any net structure are those arising from winds, waves and currents and from the interactions of the cage structure and its mooring systems with the resulting movement. Pectra or Dynema have appeared. The nets are stretched vertically with weight at the bottom of the cage or fastened by rope to the frame work. The tensile (breaking) strength of the nets can be tested to check its load carrying capacity by British Columbia Method, wherein a mesh is extended until it ruptures under the applied load. The apparatus used can indicate the load at the point of rupture. The testing machine is operated at rate of elongation which is both constant and within the prescribed limit. One important aspect in the determination of cage bag size is stocking density and optimum carrying capacity. The shape of the cage is also another point under consideration. Observations made on the swimming behavior of the fish suggest that circular shapes are better in terms of utilization of space. Corners of rectangular shapes are little utilized. It is assumed that depths greater than 10-12 m would be poorly utilized by fish and a cage depth of 3-10 m be acceptable for most of the species. Circular cages are having least perimeter for a given area, hence reducing the material cost. Fig. 2 shows the perimeter lengths of different cage shapes for the same area of 16m². Cage bag The three major functions of cage bag are a) keeping the fish stock together, b) protecting the stock against harmful external influences, and c) allowing free water exchange between the inside and outside water. The net is normally flexible and made of synthetic nylon or polythene fibers reinforced with polythene ropes although recently new stronger materials like sapphire, Fig. 2 Perimeter lengths of different cage shapes for 16m² area It is advisable to have the net meshes impregnated with a special anti-fouling material to prevent biofouling. The upper side of the cage bag above the surface is joined to the hangers in the brackets near the hand rail for lateral protection. Surrounding vertical and horizontal ropes 18 Central Marine Fisheries Research Institute From 14 - 23 December 2009 which are used for joining the net to the rings reinforces the cage bag. The cage bag comprise two nets one inner net in which fishes are placed and an outer or predator net to protect the fishes from predators. A bird net also is provided for protecting it from fish eating birds. Floats Floats provide buoyancy and hold the system at a suitable level in the surface of the water. This also holds the shape of the cage structure. Common floatation materials include metal or plastic drums, HDPE pipes, rubber tiers and metal drums coated with tar or fiberglass. Fiberglass drums are Service systems This is the system required for providing operating and maintenance services, for e.g. feeding, cleaning, monitoring or grading. One way to provide this is by a catwalk around the cage. Some cages use their floatation collars made of metal or plastic pipes with or without additional internal or external floats. But polyethylene has the strength, flexibility and lightness necessary for the catwalk in the cage. Mooring system preferred as they can last for many years although the This holds the cage in suitable position according to the initial cost is comparatively high. Styrofoam blocks covered direction and depth decided in the design. The mooring with polyethylene sheets provide good buoyancy. The joints the cage with the anchor system. A mooring system buoyant force varies depending of size and materials used. must be powerful enough to resist the worst possible Frame combination of the forces of current, wind and waves without moving the break up. Wind and current forces The frame can be made of galvanized steel aluminum, are proportional to the square of the velocity. Thus an timber and different plastic materials. The frame should increase in current from 1 knot to 2 knot will generate 4 be mechanically strong, resistant against corrosion and times the drag on a rigid submerged body. A change in easily repairable or replaceable. The cage has collars of the mooring system will change internal load on the cage HDPE for structure and the same time for floatation and system. Wave forces are much more difficult to compute for ballast. The HDPE pipes are highly flexible structure because the dynamic response of the system depends on and are used in most of the circular cages. The cage has so many factors. The materials used in the mooring line two floatation pipes filled by expanded polystyrene as a are sea steel lines, chains, reinforced plastic ropes and precaution in case of damage avoiding loss of floatation mechanical connectors. The mooring force capacity force. The ballast pipe will have holes for the free flow of depends on both the material and size and can be adjusted water and metal lines are used inside for increasing weight. to the requirements. Attachments to the system are by The hand rail pipe will not have any material inside. The mechanical connectors and ties. pipe ends will be jointed by using a welding process for plastics. Two types of mooring systems commonly used are multiple points and single point. The former is more The two pipe rings for floatation and brackets will join the common and involves securing the cage in one particular hand rail. These brackets will give support to the rings orientation while with the latter the cages are moored and at the same time it will form a part of the catwalk. from one point only, allowing them to move in a complete The brackets made of galvanized steel to avoid corrosion circle. Single point mooring tends to be used with rigid and be fitted to the diameter of the pipes. The maximum collars. They use less cable and chain than multiple point height of hand rail should be approximately 100 cm and mooring and, because they adopt a position of least minimum width for cat walk approximately 60 cm. resistance to the prevailing wind, wave and current forces, 19 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi both inter cage forces and tortional forces at linkages are reduced. Single point mooring system also reduces the enormous net deformation than the conventional mooring system. They distribute wastes over a considerably larger area than those secured by a multiple point system. Fig. 3 & 4 shows single and multiple point mooring systems. To avoid the possibility of bag shape deformation caused by possible high currents, the mooring uses a system of six joint points to the cage, three in the upper side to the floating pipe and the other three in the lower side attached to the ballast. This connection up and down in the cage assures to maintain the shape in position irrespective of the currents. The orientation of cages with multiple mooring depends on the nature of the site and the type and group configurations of the cages. If the currents are strong it may be best to secure cages in the position of least resistance to the prevailing wind and current force, Fig. 3 Single point mooring system There are a variety of methods of using a single and multiple point moorings. mooring system are principally dynamic. It is important that mooring line must have a high breaking strength and can absorb much of the kinetic energy of rapidly changing forces (wave and wind) otherwise these forces will be directly transmitted to anchors. Chains are used as mooring line, it is extremely stronger but it is heavy and used in conjunction with synthetic fiber rope, Synthetic fiber ropes are composed of nylon, PE, PES, PP etc. Stainless steel chain is suitable for marine use, but it is expensive. Mild steel chain with low carbon and manganese contents has been widely recommended for cage anchorages. Total length of the mooring line should be at least three times the maximum depth of water at the site and where the rope joins the chain a galvanized heavy duty thimble should be spliced in to the rope and a galvanized shackle of the appropriate size used to connect the chain to the rope. The chain is connected from the anchor to a float positioned 10 m or so from the cage and a section of rope is used to link the float to the cage. The buoy minimizes the vertical loading on the cages and must be sufficiently large to support the mass of the chain and to resist the vertical forces imposed by the cages on the mooring system. Under shock loads, the chain /buoy acts as a spring absorbing much of the energy that would otherwise be transmitted to the anchor. The possible shock loads can be counteracted using a system of hung weights located between the multi connector pipe and the anchor. This system ensures soft movements of the cage with the current by absorbing possible shocks. The vertical position of the weights depends on the forces acting upon it, thus operating as a shock absorber. Anchor system Fig. 4 Multiple point mooring system Mooring line must perform two functions: they must withstand and transmit forces. The loads imposed on a cage The simplest and cheapest type of marine anchor is the dead weight or block anchors, which typically consist of a bag of sand or stones or a block of concrete or scrap metal. Concrete block anchors may simply be fabricated with reinforcement. The anchor is connected to the mooring system by chains and ropes. The anchor system is normally formed by a system of concrete blocks joined together, by chains and connected to a buoy by a braided rope. Several concrete blocks instead of one, make the 20 Central Marine Fisheries Research Institute From 14 - 23 December 2009 setting of the system easy. These mooring and anchor systems allow the cage to be disconnected easily and quickly in case of bad weather and the cage can be towed to a safe place without loosing its shape. Mooring maintenance Cage mooring is a dynamic system which must respond to motion under load every minute of the period for which it is established. Maintenance is critical to ensure that components are physically sound and that linkages secure. Wear and tear of the parts namely chain links, brackets, shackles, splicing eyes, need to be checked periodically and bolts and shackle pins need to be tightened. Proper maintenances of the entire system gives more life to cages. Specifications of the CMFRI cage at Munambam, Kochi The chosen site was having an average velocity of current 1m/s, depth 10 m, and muddy sea bottom. The loads were divided in to two types: a) Static loads, which are vertical and are caused by the action gravity with reaction in the buoyancy of the cage. These depend on the area and density of the netting, weights of the frame components, weight of rigging, weight of the ballast and opposition in the floatation force. b) Dynamic loads, which are mainly horizontals and are caused by the current, winds and waves with reaction in the moorings and anchors of the cage. These depend on the materials used, shape of the panel, size of the mesh, current velocity and density of water. To compute the static loads in the cage the relation between the weight of the cage with its components like the descendent force and the capacity of floatation the ascendant force was estimated. The weight was computed for three conditions: a) Clean cage in air b) Clean cage in water c) Foul cage in water In order to compute the weight of the cage in water, the densities of the materials used must be established. For the cage to float, the static loads acting on the structure ( i.e. weight in water) must be counterbalanced by buoyancy forces. The buoyancy of the collar is dependent upon the upward force acting on those components wholly or partially immersed in water and is equal to the weight of water displaced. The buoyant forces can be calculated by using the formula: FB = Vw Qw-Vm Qm FB = buoyant force (kg) Vw & Vm are the are the volumes of water and floatation material (m³) Qw & Qm are the densities of water and floatation material (kg/ m³) The loads caused by the currents, wind and waves against the cage were considered to be the dynamic forces. These forces act on different parts of the cage, but all of them drag and deform its shape. The knowledge of these forces is required for the computation of the mooring and anchoring system. The current act mainly on the cage bag and rigging under the water, the load depends on the current velocity, density of water, material, shape and size of mesh. Water flowing through a mesh or netting imposes loads which are transmitted to the supporting frame, collar and mooring system. Wind and current forces are proportional to the square of the velocity. Thus an increase in current from 1 knot to 2 knot will generate 4 times the drag on the rigid submerged body. Wind forces act mainly on the cage superstructure formed by hand rail, brackets and free board netting. 21 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi The general equation to calculate the current drag is Fx = 1/2 Cd.µAv² (expressed in KN) Where Fx = current drag Cd = coefficient of drag p = density of sea water in T/m³ A = area normal to flow in m² V = incident current velocity m/s The wave forces acts mainly in the ring area of the cage. It is very difficult to compute the wave forces as the dynamic response of the system depends on so many factors. To calculate it, the horizontal and vertical orbital velocities of the water particles must be known. These can be derived from the information on prevailing wave periods, wave height and water depth at the site. Wave force (Fw) = Kd.pµ²A Where Kd is the coefficient similar to Cd in netting whose value depends on the material and shape of the collar p = density of sea water µ = horizontal component of wave particle orbital velocity (for marine cage it s taken as 2m/s) A = area of the cage collar perpendicular to the wave train The moorings and anchor system and their components were proposed based upon the calculated forces on the cage. For a particular current velocity a fouled cage with total load (sum of the loads acting on each component) was calculated. Based upon the maximum load estimated a gabion box made of PP with copper lining containing three compartments of 1t each (total 3t) capacity was filled with stones and used as the mooring system. Specifications of other materials used for the cage are given in Table 1. Table 1 Specifications of the parts used: Part Material Size /quantity Floating pipe innerFilled with PUF HDPE140mmø 10kg/cm²(PE100 grade material 6m dia Floating pipe outer HDPE140mmø 10kg/cm²(PE100 grade material 8m dia Middle ring HDPE90mmø 10kg/cm²(PE100 grade material catwalk Base supports 250mm,HDPE 8 nos. Vertical supportsFixed with T joints , using fusion welding as well as with SS bolts and nuts 90mm,HDPE 0.8 m height16 hooks Diagonal support 90 mm, HDPE 10 kg pressure 8 nos Buoys,filled withPUF, 350mm dia with end caps(10 kg) Mooring clamps 14mm,4"mooring clamps Mooring chainMS 10mm 3 nos Ballast pipe HDPE,63 mm ,circular Mooring swivel MS Outer net, Braided HDPE, 3mm/80mm square mesh Provided with SS rings of 12mm thickness,for connecting to the cage frame 7m dia&5m depth, 18 rings bottom12 ring top Inner net, Twisted HDPE net 1.25 mm/30-35mm mesh size With SS rings 6m dia & 5.3 m depth12 rings top Bird net,1.25mm/80 mm twisted HDPE 6m dia Hapa,Nylon with 8/10 mm mesh 2.5x2.5x3 m rectangular shape Chain 80 grade MS 10mm 3T working load,7T stretching load,11 breaking load D shackle 1’’,1/2’’&3/4" MS (3T,0.5T,3Tworking load) Swivel 1’’ forged steel 80 grade 3T working load Solar blinkers Water proof shock resistant red colour blinking light 8m dia 3 Nos 22 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Netting specifications and maintenance of cages for finfish culture Saly N. Thomas Fishing Technology Division Central Institute of Fisheries Technology, CIFT Junction, Matsyapuri P.O. Cochin - 682 029, India, salynthomas@gmail.com A cage is a space enclosed with some type of mesh or 5×5 m, with a depth of 2-3 m while rectangular types are forming a container for aquatic animals to grow. It is 6×3 m, with a depth of 3 m. In Korea, the floating cage typically box-shaped or tube like structure with a rope system consists of the cage and a frame to support the system which supports the netting material, gives shape nets. In India, rectangular cages of 10mx5mx2.5m are used and allows for tying to the raft unit. In box type cages, for the culture of Indian major carps. the cage is constructed of four panels at the sides and one bottom panel. Anti-predator nets are deployed around Basically there are 3 types of cages: the cage to prevent entrance of predators such as sharks Hapa cage is for stocking of the fish during the early and sea lions into the cages. An additional net would be nursery phase (Fingerlings to a Total Length of about 10 provided on top of the cage to prevent bird predation. cm). This is made of very fine-meshed nylon net. It is used for rearing fry to fingerlings. Fry measuring 1–6 cm Types of net cages are initially stocked in this cage. The cages usually are of two types: fixed and floating. Nursery cage is used during the later nursery phase. The floating cages are interlocking cages suspended in a Usually PE net is used for the net bag. This cage is stocked bamboo/wooden/ polyethylene frame. The cage is floated with 10 cm fingerlings till they reach a size range of 15– by either bamboo raft or styrofoam floats, and is held in 20 cm. place by heavy anchors. Grow-out cage is used for the grow-cut phase where The dimensions and mesh sizes of the cages are dependent the cultured fish reach marketable size of 30 cm and on the species cultured and size. The mesh sizes of the cages beyond. The netting used is usually PE net. depend upon the type of cage. In Japan, circular and square/ rectangular floating cages are used, whereas in Norway floating cages are not only circular, square/rectangular, but Broodstock require cages of mesh sizes larger than 50 mm. may also be hexagonally shaped. Cages that are either The rope which is used for the main and hanging lines of cylindrical or spherical are used in West Germany. In the hapa and nursery cages is PP/PE rope (6 mm diameter), Singapore, the farmers use the more conventional square while for the grow-out cages, PP/PE rope of 10 mm (cuboidal) cages. The square type usually measure 2×2, 3×3 diameter is used. 23 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi The frame which is used to hold the interlocked cages forces on a net impoundment structure are based on the together in place also serves as a catwalk and working highest wave expected to occur in the design life of the platform. A frame made of bamboo is preferred over a structure. As fouling or surface debris drastically affect wooden one mainly due to economic reasons. Besides, the coefficient of drag, this factor must be considered. the bamboo frame also acts as a floatation device. Fouled nets create twice the resistance to tidal current as the same net when clean (Milne, 1970). The nets must As net bags are subject to damage by floating debris, large be designed to withstand the sum of the forces, assuming carnivorous animals and other agents, often a second that all the forces are at some moment acting in the same larger mesh net is used outside the net to provide direction. If two nets are used, loads on the supporting mechanical protection for the confinement net. The two structures will be the sum of the loads imposed by each nets must be placed in such a way that they do not rub net. each other, or one or both nets will be damaged by abrasion. E.g: the outer netting can be of HDPE braided twine of 3 mm diameter and mesh size 80 mm. There can be an upper selvedge of netting made of HDPE of 4 mm diameter braided twine of the same mesh size and 80 mm mesh size. This selvedge portion should be of 0.5 meter stretched length or equal to the length of the brackets/rings above the upper ring structure whichever is larger. Inner netting can be of HDPE twisted twine of 1.25 mm diameter and of mesh size 25 mm. An upper The aquacultural net enclosures should have good tidal flushing. Water flowing through the net will impose loads on the net and supporting or mooring structure. Kawakami (1964) developed the following Equation 12.9 to describe the load imposed on net structures due to flow at right angles to the net. The force on 2.50 cm mesh nylon net by a 1 m/s current is 0.42 N/mesh in the unfouled condition and 5.1 N/mesh after one month of immersion in sea water. selvedge of netting made of HDPE twine of 2 mm diameter Nets enclosing fish are subject to damage by floating and with 25 mm meshsize. This selvedge portion should debris, large carnivorous animals and other agents. A be of 0.5 meter stretched length or equal to the length of relatively small hole in the enclosure net can result in the brackets/rings above the upper ring structure loss of nearly all the fish. Hence, it is often wise to use a whichever is larger. second larger mesh net outside the confinement net to provide mechanical protection for the confinement net. Design Considerations The two nets must be placed in such a way that they do Designing of net structures require several forces to be not rub each other, or one or both nets will be damaged considered; the main being static and dynamic loads. by abrasion. As all nets require periodic maintenance for Static loads include the weight of the structure (net, cleaning or repair before design it must be decided support, and other structural parts), and added loads due whether the panels will be pulled out of the water for to maintenance and operations. Dynamic loads include this work or divers will be used. If the panels must be forces generated by wind above the water surface, waves removed from the water, some means to prevent fish at the air-water interface, and currents (particularly tidal escape will be necessary. The panels must also be small currents) in the water. Additional dynamic loads may be enough to be manipulated by the handling technique encountered due to collection of floating debris, collision chosen. Panel weight will be actual panel weight plus with water craft or large predators or other similar weight of fouling. The following factors are generally conditions. Effects of corrosion and fouling add to it. Wave considered in the design and operation of culture cages: 24 Central Marine Fisheries Research Institute From 14 - 23 December 2009 z z It is advisable to put floating cages underwater to avoid netting without further process, hence it follows that wind action and also to reduce algal growth monofilament yarn is a netting yarn also. The Twisted Use cage materials available within the locality to reduce the costs z netting yarns (netting twines) are made by a series of processes. z Fibres twisted together to form a single yarn. z A number of single yarns are twisted together to form Before setting out the antifouling impregnated nets they should be dried so that the antifouling stays on a strand or ply. the net. z Consider the cost and durability of the materials z Net size: It is better to design the size of net cage to suit the breadth of the netting rather than on a preselected size. z z Three strands or ply are twisted together to form a netting twine. Synthetic materials are predominantly used for construction of net cages. Synthetic fibres are produced entirely by chemical process or synthesis from simple Size of species: Net mesh should be smaller than the basic substances such as phenol, benzene, acetylene etc. fish size to avoid escape of the fish through the As compared with vegetable fibres, they have better meshes. uniformity, continuity, higher breaking strength and are more resistant to biodegradation. Depending on the type z z Nets should have sufficient strength to withstand of polymer, synthetics are classified into different groups different forces encountered and are known by different names in different countries. Net bag should have suffiecient looseness. To get a uniform spreading and flexibility to the bag 20-30% of excess net is to be used than the actual cage size z Aeration can enhance water quality, reduce stress, improve feed conversion efficiency and increase growth and production rates. Aeration can improve cage production by 20 percent or more. z Altogether 7 groups are developed; polyamide (PA), polyethylene (PE), polypropylene (PP), polyester (PES), polyvinyl chloride (PVC), polyvinylidene chloride (PVD) and polyvinyl alcohol (PVAA). The synthetic netting yarns used in Indian fisheries sector are polyamide, polyethylene and polypropylene. PA and PE are the most commonly used fibres for netting while PP and PE are used for ropes. The material strength of Leave at least 10 feet between cages and keep cages net panels when exposed to sunlight (UV), wind, rain, away from weed beds. Weed beds and overhanging acid rain, etc. get reduced. This process is called trees can reduce wind circulation and potentially cause weathering. Even though all fibres, irrespective of natural problems. or synthetic are prone to degradation on exposure to weathering, the problem is severe with synthetic fibres. Netting materials for cage construction The main factor responsible for weathering is the sunlight, Netting yarn is a textile product suitable for the i.e. the ultra violet part of the sun’s radiation. Polyvinyl manufacture of netting and can be knitted into netting chloride (PVC) is the material that is most resistant to by machine or by hand without having to undergo further weathering, followed by PE and PA; PP has the shortest process. Yarn is made into a netting by twisting or lifetime. The lifetime can be increased by adding a braiding. Monofilaments are used directly for making into coloured (black) antioxidant, so that development of 25 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi weathering is reduced. The resistance of netting materials Polyethylene is preferred for its high breaking strength, to abrasion, i.e., abrasion with hard substances such as durability, high resistance to abrasion and cheaper cost frames, sea bottom and net haulers, or abrasion between when compared with other available materials like yarns/twines is important in determining the life of a net. polyamide, polyester, polypropylene etc. Another material recently introduced is Ultra high z Polymide (PA) and polyethylene (PE) netting are readily molecular weight polyethylene (UHMWPE) available as available locally. Knotless polyamide netting of Dyneema. It is very advantageous as aquaculture nets 210Dx2x2 is popular for making cages that are to be due to the low diameter, favorable weight/strength ratio, used for stocking young fish fingerlings and prawns low elongation and nil shrinkage in water which helps as the material has a smooth surface and there is the mesh size to remain stable during normal use of the minimal abrasion on the fish when the cage is lifted netting. The resistance of Dyneema nets to UV light and up during net change. PA is expensive and costs about abrasion is high, guaranteeing that nets last longer. Rs. 350-470/kg. However, it has a very high breaking Selection of netting material strength and abrasion resistance. Its fibre deteriorates if subjected to prolonged direct sunlight and hence it The following factors are to be considered for selection is classified as having medium durability. The material of suitable net material for the construction of cages: being soft, can also be cut through by crabs and fish Synthetic fibres are preferred over artificial or natural fibres with strong dentition and the cultured fish can escape because of their durability and strength. z through gaps made in the cage Cages made of synthetic fibres are convenient to use as they can be easily folded and are light to handle. z operators because it is cheaper and protects better They are also easy to install and to remove. It is not against damage caused by crabs and fish, although surprising that many floating farms use such materials large-sized crabs can still bite through the material. It rather than rigid metal cages for rearing the fish z is the cheapest of the synthetic netting materials The netting yarn should maintain its shape, e.g. available, priced at around Rs. 200-275/kg, viz. around monofilament netting, suitable for gill-netting, is not half the price of PA netting suitable as cage material as it tangles and folds up easily z z z PE netting is available in various specifications of Denier and ply and also in knotless and knotted forms. The material should be durable, resistant to abrasion The type that is selected would depend on the species and has high breaking strength and size of fish stocked. PE has also high breaking The material should not be so heavy as to make handling difficult e.g. thicker netting material even though durable and resistant to crab bites/abrasion would be heavy at cleaning time especially when it is fouled. z Polythylene netting is generally preferred by cage strength and abrasion resistance. However, like PA, it is to be stored away from direct sunlight, viz. in the shade. When used at the farm, the portion of the cage above water lasts for 3 years, whereas the rest of the cage which is submerged in the water lasts for 5 or more years. PE netting is usually for making cages for With the exception of the hapa net, cages are usually nursery and grow-out fish while for hapa, PA is constructed of polyethylene (PE) material. preferred 26 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Table below lists the synthetic fibres that are suitable for distance between the knots on a stretched mesh (Fig. 1). use as fish cages. In a hexagonal mesh, the mesh size is given as the distance Table 1 Comparison of important characteristics of synthetic fibres Properties PA PE PP PVC PES PVD PVA Specific gravity 1.14 0.96 0.91 1.35-1.38 1.38 1.70 1.30 Melting point °C 240-250 125-140 160-175 180-190 250-266 170-175 220-230 Durability Medium Medium Poor Very high High High High Breaking strength Very high High Very high Low High Low Medium Extensibility (wet) High Medium Low High Low High High Resistance against weathering Medium Medium Low Very high High High High Abrasion resistance Very high High Medium High High High High Cost Very high Low High High Very high High High polyamide (PA) is the most commonly used material for between the two longest parallel bars. Mesh size may, the fabrication of net bags, as the material is strong and however also refer to bar length, which makes this not too stiff to work with. PE is also used to some extent expression rather confusing. because it is more resistant to fouling as the surface is smoother: however, it is stiffer to work with. Polyester (PES) has also been tried. Nylon used for nets is made as a multifilament twine consisting of several thin threads spun together to make a thicker one. The advantage with multifilament is that the thread is easy to bend, easy to work with, tolerates more loads and is more resistant to wear/rubbing. In contrast, monofilament is a single thread as used in a fishing line. It can be made of PE; it is stiffer and more vulnerable to chafing than a multifilament. Nets are either knotted or knotless. Mesh size Another factor which decides how the net panel is standing in water is how the net is stretched in the length and depth wise directions. This is called the hanging ratio of the net (E) which is the ratio between the length of the stretched net panel (Lm) and the length of the rope/ line where the net is fixed (top line) (L): E = L / Lm Normally E for net bags for fish farming is in the range 0.6 – 0.9, while for a fishing net, E is between 0.4 and 0.6, meaning that netting of cages have meshes that are more stretched out (Fig. 2). Mesh size can be described in many ways. Bar length is the distance between two knots while mesh size is the Fig. 2. Hanging ratio and corresponding vertical mesh opening Solidity is used to describe the ‘tightness’ of a net. This is the ratio between the total area that the net covers, compared to the area covered with threads including knots. This relation is important when the resistance Fig. 1. Mesh size against water flow through the net is to be calculated. 27 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Fouling on the net will increase the solidity, because the z covered area is increased. completely in water to form a diamond-shaped hole so as to allow good water exchange with minimum Mesh-size selection is dependent on the species and size use of netting material to be stocked. The seabass, having a more pointed snout would require a cage of smaller mesh-size than would a z Meshes should not be large enough to gill the fish stocked grouper of the same size. The relationship between cage mesh size and a few fish species are summarized in Table z 2 and recommended material amd mesh size for different Mesh size should be roughly equal to about 25% of the body length of the fish cage types are given in Table 3. Construction of cages Factors to be considered for mesh size selection z The meshes of the cage should remain open Mesh size should not be less than 10 mm to assure Hapa cages good water circulation through the cage while holding The dimensions of the hapa cage can range from 2×2×2 relatively small fingerlings (10 to 12.5 cm) at the start m to 3×3×3 m to 5×5×2-3 m depending on the scale of of the production cycle. stocking. Mesh size can range from 8 mm to 9.5 mm Table 2 Relationship between cage mesh size and fish species Type of cage and netting material Mesh-size (cm) Grouper, TL (cm) (Epinephelus tauvina) Seabass, TL (cm) (Lates calcarifer) Snapper TL (cm) (Lutjanus johni) 5–10 10–15 15–40 40–50 50–75 75 and > 7.5–10 10–25 25–30 Broodstock Broodstock Hapa (PA 4 ply) 8 Nursery (PE 15 ply) 13 Production (PE 24 ply) + >30 5–10 10–15 15–2050 and > Broodstock + + + + 25 + 25 + 50 + + + + + 75 + + + + 100 + (Source: FAO, 1988) Table 3 Recommended material and mesh size specifications for different cage types Cage Recommended material specifications Mesh Size (mm) Fish size recommended(TL, cm) Grouper Seabass Hapa Polyamide (nylon) 210D/2x21200 meshes deep. 9 5–10 10 and < Nursery Polyethylene, 380D/2x3300 meshes deep. 9.5 10–15 10–15 Polyethylene, 380D/3x3 or 5x3300 meshes deep. 12.7 10–15 10–15 Polyethylene, 380D/5x3 or 6x3300 meshes deep. 19.1 15–30 15–20 Grow-out Polyethylene, 380D/6x3 or 7x3300 meshes deep. 25.4 15–40 20–30 Polyethylene, 380D/7x3 or 8x3300 meshes deep. 25.4 15 – 40 >30 Polyethylene, 380D/9x3300 meshes deep. 38.1 15–40 >30 Polyethylene, 380D/10x3 or 11x3300 meshes deep. 5.8 40–50 - 28 Central Marine Fisheries Research Institute From 14 - 23 December 2009 depending on the initial size of fry/fingerling stocked. The z The dimensions of the cage should be slightly smaller hapa cage is usually constructed of knotless material, e.g., than the floating frame on which it is suspended so PA, so as to avoid any abrasion to the fish fingerlings that the cage fits well within the frame. during hauling of the cage. Knotted netting should be avoided as far as possible as the abrasions caused to the z the meshes required that would give the desired fingerlings could result in disease, especially bacterial vertical mesh opening or hanging. Stretching the infection. Besides, small-mesh knotted netting materials material to the actual cage dimension will result in are also heavy and easily fouled as fouling organisms tend uneven measurements and irregular fit. to be congregated to the knots. Main rope is made from PP/PE of 5–6 mm diameter. Bolch line is usually made of Cutting: Synthetic nets are to be cut by calculating z Vertical mesh opening or hang-in of the netting must PP/PE of 2 – 3 mm diameter. PA netting twine of 210D/ be pre-determined. The vertical mesh opening or hang- 9x3 is used for hitching the bolch line to the main rope, in of the netting is defined as the mesh size of the and 210D/6x3 is used for joining the netting material/ netting at free hanging and is expressed as a panels/sections to the bolch line. percentage. Nursery cage Like the hapa, the nursery cage can be of 2×2×2 m, or 3×3×3 m, or 5×5× 2-3 m, depending on the scale of z A vertical mesh opening or hanging of about 70 % is recommended for cages as the mesh then approaches that of a square as seen in Fig. 2. stocking. The netting material used is usually of the The side net panels are joined to the bottom panel by knotted type. Polythylene (PE) is usually selected. Mesh sewing with twine. Sewing is done by passing the twine size can range from 9.5 mm (3/8") to 25.4 mm (1") along the outer edges of the two panels in a 1 mesh side depending on size and type of fish stocked. Main rope is to 1 mesh bottom ratio. For every 5 stitches, an overhand PP/PE of 8 mm diameter while bolch line is also PP/PE of knot is made. A bolch line is to allow the attachment of 2mm diameter. PE twine of 380D/4x3 is used for joining the main rope to the netting material. It is passed along the netting panels and 380D/6x3 or 7x3 is used for joining the 4 bottom seams of the cage between the side panels the bolch line to the main rope. and bottom panel (basal bolch) and along the top square Grow-out cage Cage dimensions of grow-out cages are similar to hapa and nursery cages. Like the nursery cage, grow-out cages are also constructed of knotted netting, usually of PE material. of the side panels (top bolch). Threading is done through each mesh, if necessary. The bolch line is a thin rope whose diameter varies according to the netting material used. Mesh sizes start from 25.4 mm (1") and mesh size to be The main rope is used for giving the cage its shape and selected depends on the size of fish stocked. Larger sized for suspending the cages. It is sewn on to the bolch line. fish of 30 cm could be stocked in cages of mesh size 50.8 It is of a larger diameter than the bolch line and its size, mm. The main rope is PE of diameter 10 mm. Bolch line, as like the bolch line, varies according to the netting material for nursery cages, is of PP/PE of 3 mm diameter. used for the construction of the cage Factors to be considered for cage construction Maintenance of the cage z The net panels should be cut such that there is The normal lifetime of a net bag will vary with the site minimum wastage of netting material conditions.. As a general rule, if the breaking strength of 29 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi the net bag below the surface falls below 65% of the initial affected by salinity, water depth and substrate area and strength it is considered as unserviceable. With proper immersion period. care, cleaning and repair, the economic life of polyethylene nets ranged from two to five years. The small mesh size net of less than 2.4 cm foul more rapidly and has to be cleaned more frequently. In temperate regions, the life time of a net bag is usually 5 years. Biofouling Biofouling is a major problem in cage culture during summer months especially at marine sites. Biofouling occurs as a result of the settlement and growth of sedentary and semi-sedentary organisms like barnacles, tunicates, tube worms, mussels, bryozoans and algae on artificial structures placed in water. It mostly composed of organisms with organic or mineral material trapped in between. Floating cage culture using nets is particularly Multifilament netting material is particularly vulnerable to fouling, as it is non-toxic, contains many crevices that can entrap and protect settling organisms, and has a high surface-area to volume ratio. The materials used for making the nets (metal, synthetic materials) and their form (galvanized panels or nets) also affect fouling levels. Galvanized panels developed much less fouling than the synthetic fibre netting panels. Since fouling encrusts small mesh nets more rapidly, the fish farmer should use the largest mesh size permitted by the size of the fish. Netting colour significantly affected the growth and composition of algal fouling, but had no effect on invertebrate fouling. Fouling Control vulnerable during the hot season. Although biofouling of The prevention of fouling on mariculture structures is artificial substrates has been well studied, biofouling complicated by the choice of net material and the dangers pertaining to the aquaculture environment and biofouling of toxins to cultured species. Antifouling practices include on cages in tropical marine waters is less studied. The predominantly the use of copper-based antifouling frequent cleaning of nets is not only costly and labour coatings. There have been incidents where antifouling has intensive but often gives rise to loss of stocked fish due adversely affected fish: in the 1980s, trials with tributyl- to net changes and damage. Uncleaned nets on the other tin on cages caused significant effects to farmed salmon. hand can cause severe physical stress on the cage nettings The antifouling solutions presently available are not ideal, during strong current flow when they could tear. Fouling and it is widely accepted that there is an urgent need for significantly impedes the water flow and therefore the research into anti-fouling technologies. Such alternatives supply of dissolved oxygen to the caged fish. Fouled include the adoption of “foul-release” technologies and netting also increases structural fatigue on cages and the “biological control” through the use of polyculture fouling communities may harbour disease-causing systems. However, none of these have, as yet, been microorganisms. Hydrodynamic forces on a fouled net can proven satisfactory. In view of current legislative trends be 12.5 times that of a clean net. Concurrently, the weight and the possible future “phasing out” of available of cages can increase sever-fold, causing further structural antifouling materials, there is a need to find alternative stress as well as a reduction in cage buoyancy and strategies. The use of most commercially available, increased net deformation. Retarded water flow and antifouling chemicals or coatings on cage nettings is inorganic and organic enrichment through fish feeds and largely restricted due to concern of environmental faecal matter enhance the macrofouling assemblage on toxicity. For these reasons, the natural control of fish netting. The structure, colonization dynamics and biofouling or environment-friendly methods is to be used. depth distribution of the macrofouling assemblage are Such methods require a better understanding of the 30 Central Marine Fisheries Research Institute From 14 - 23 December 2009 fouling community of cage netting, particularly how it Cage cleaning: The nets should be cleaned regularly to interacts with the physical environment and aquaculture prevent excessive fouling that may result in net breakage itself. It has been recently demonstrated that silicone and heavy losses of fish. The smaller the mesh size, the coatings provide an effective non-toxic solution to reduce heavier the rate of fouling. Nets of mesh size less than fouling on sea-cages and to increase the ease of fouling 2.5cm should be cleaned within 1 or 2 weeks of use removal. whereas the larger size nets need to be cleaned in 30 to Fouling organisms of the cage can be controlled biologically to some extent by using grazer fish species 90 days. Fouling organisms are removed by a high pressure water jet. within the culture fish. Grazing by wild fish and other Cage drying: The cleaned net is checked for holes and predators could also contribute to the slower colonization repaired before it is used again. It can also be hung-up to rates outside the cages. The introduction of predatory dry and mend in position. fishes or sea stars could provide some amount of control on the growth of fouling organisms. Cyprinus carpio consume algae on nets and in the cage. Thus polyculture, when it is possible, may be a solution to limit fouling development in some sites. Cage mending: Net panels may get damaged or ropes may become weakened from frequent use. Panel and roped replacement or partial replacement with rejoining may be required, in such cases. Due consideration need to be given for the design, Abrasion construction and maintenance of the cage for the success Abrasion of the netting with fishes, with the rafts and of cage culture. Selection of suitable netting material, frames as well as between inner and outer net in cases fixing of optimum mesh size and periodic maintenance where double netting is provided are problems of the net bag are the most important parameters to be encountered. It is a common practice to have double taken into account. Focused research is needed on netting. The outer one serving as a predator net, to protect selection of netting materials, optimization of cage design the inner net with the fish stock. and construction for different species and culture sites and on fouling control measures. In cases where the netting has a chance of rubbing with the frames or brackets, provision of a selvedge netting of References same mesh size but of thicker twine would avoid the breakage of netting along the point of abrasion Aqua Farm News, Vol X No.3 (May-June 1992), Bureau of Fisheries and Aquaculture Resources (BFAR) Regional Office. Maintenance procedure Beveridge, M.C.M. 1987. Cage Aquaculture. Fishing News Books Ltd. Farnham. Surrey. UK. 352 pp. Maintenance of cages involves net changing, cleaning and mending. Cage changing: The frequency of change depends on the mesh size of the cage and the season for fouling organisms which cause the cage to clog. As cage changing is time consuming and laborious, a mechanised net hauler may be considered for lifting out heavily fouled cages. FAO 1988. Training manual on marine finfish cage culture in Singapore, FAO, Rome FAO.1988. Seminar report on the status of marine finfish cage culture in China, DPRK (Democratic People’s Republic of Korea), Indonesia, ROK (Republic of Korea), Malaysia, Philippines, Singapore and Thailand Kawakami, T. 1964. The theory of designing and testing fishing nets in model. In: Modern Fishing Gear of the World (H. Kristjonsson, D.), Fishing News (Books) Ltd., London. 31 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Klust, G. 1973. Netting materials for fishing gear. FAO Fishing Manuals, Fishing News (Books) Ltd, London, England, 173 p. Lekang, O. Aquaculture Engineering, Blackwell Publishing Ltd., UK. 340p. Milne, P.H. 1970. Fish farming: a guide to the design and construction of et enclosures. Mar. Res. Bull. No. 1. Department of Agriculture and Fisheries for Scotland. Edinburgh Nash, C.E. 1988. A global overview of aquaculture production. J. World Aquacult. Sot., 19(2), 51-58 32 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Principles and practices of cage mooring Boby Ignatius Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India bobycmfri@yahoo.co.in Moorings are required to hold cages against the forces Mooring requirements should be determined by the design generated by wind, currents and waves and to allow the and type of the cages and the characteristics of the site. fish stocks and the cages and let the best chance of It would first be necessary to quantify the incident forces survival. In sheltered waters, requirements to moor a cage that are likely to act on the cage under the worst possible safely were minimal. This has changed dramatically with weather conditions, and then to evaluate the proportion moves into coastal waters, and a potentially much higher of energy transferred to the mooring lines and anchors. wave climate. Mooring failures were common place in the Two types of analysis can be used: quasi static and early days of coastal farming, but a better understanding dynamic response. The loadings transferred to mooring of the problems, and more sophisticated analysis has lines vary enormously depending on current and wave largely reduced these risks. Perhaps the most important conditions, cage design and number of lines employed. point is to view the cage group, its nets and moorings, as a single system, whose components are mechanically Mooring design for a specific cage system and site linked. Their dynamic responses cannot be considered in Wind and current forces are proportional to the square of isolation, each component affecting the other. Cage and the velocity. Thus an increase in current from 1 knot to 2 mooring design is “site specific”, and careful and combined knots will generate 4 times the drag on a rigid submerged choice of cage type, nets and most specifically moorings, body. Wave forces are much more difficult to compute, has a considerable bearing on the ability of fish stocks to because the dynamic response of a system depends on survive in major storms, on exposed sites. so many factors. A change in the mooring system will Most moorings systems consist of lines and anchors that change the internal loads on the cage system. This is a secure cages in a particular location. However, the complex topic, but in general a mooring system should moorings also influence the stress acting on cage be designed not only for specific cages, but also for the structural members and the behavior of the cages in rough expected site conditions of water depth, wind, waves and weather, and can affect production, profitability and staff current. safety. They are therefore an important - indeed, integral part of the cage system and should be carefully designed. Mooring components Thus the collar, net and mooring components of a cage Whichever type of mooring layout is employed, a number system should be designed together, although in practice of elements need to be assembled together, correctly the cages are usually chosen or built first with the mooring specified and installed, physically and operationally system being designed as an afterthought. compatible with each other, and effective in use and 33 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi maintenance. Key elements include the anchor or mooring attached, so that they can be floated to the required unit on the seabed, the rising line, which connects the location at high tide. Once installed, they are difficult to anchor to the surface system, and the surface or recover. subsurface mooring grid. The major elements comprise several smaller sub-units – particularly links, shackles, droppers, safety lines, buoys, etc., which in effect are integral in the complete system. There are numerous types of embedding anchor. The holding power of an embedding anchor is related to its frictional resistance in soil, and so is dependant on fluke area, soil penetration and the mechanical properties of Anchor specifications the soil rather than simply the mass of the anchor. A range of different types is available, commonly from Embedding anchors are very efficient, i.e. they have a high the shipping/fishing industry. Major options are usually holding power to mass ratio. Under optimum conditions, between gravity or dead weight devices – mooring blocks they are 10-500 times as efficient as block anchors. They or mass anchors, which rely primarily on their weight, and are more expensive than block anchors in terms of cost those which rely on their ability to wedge into the seabed per unit holding power and have to be bedded in properly. substrate. Blocks are widely used because of their The use of two anchors connected together gives greater simplicity, their stability to tension in all directions, and holding power than the sum of independently moored their relative ease of positioning and relaying, but their anchors. There are numerous other type of anchor, efficiency is low. Gripping devices are much lighter and combining the properties of block and embedding types, more efficient in the appropriate substrates – e.g., muds while others are designed for particular types of substrate. and shingle mixes, but need to be properly tensioned; once bedded in they can also be difficult to reposition. The simplest and cheapest type of marine anchor is the dead weight or block anchor, which typically consists of a bag of sand or stones or a block of concrete or scrap metal. The holding coefficient of the anchor (k) is defined as (R) the horizontal force divided by the mass of the anchor. The holding coefficient (k) depends upon the angle between the anchor and the cage and thus the ratio between water depth and line length and the nature of the substrate. Prior to choosing or installing anchors it is advisable to survey the sea bed. Anchors should be positioned first. The position of the anchors can be accurately established using a global positioning system or by taking bearings with respect to local. Easily visible land marks. Rising line components A range of materials and configurations may be used, the most common of which involves a chain section at the lower end of the line, a synthetic rope in the main upper length, and various elements of buoyancy or weighting Block anchors have low holding power per unit-installed to adjust the profile of the line, and its response geometry weight. The performance of a sand bag anchor is much when subject to varying load. A range of different types poorer in mud. Concrete block anchors may be simply and specifications may be available for chain and rope. fabricated using wooden shuttering, tyres or any other Key issues concern weight and tensile strength, elasticity convenient object as mould. Steel rods for strengthening (length change with applied tension), stretching, and eyebolt for a mooring attachment are usually dimensional wear, degradation. Float units need to be incorporated. Once fabricated, the blocks can be specified according to volume and shape, and to their transported to the waters edge at low tide and floats resistance to deformation when submerged. 34 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Mooring lines must perform two functions: they must The total length of the mooring line should be at least withstand and transmit forces. The loads imposed on a cage three times the maximum depth of water at the site and mooring system are principally dynamic. It is important that where the rope joins the chain, a galvanized heavy duty mooring lines have a high breaking strength and can absorb thimble should be spliced into the rope and a galvanized much of the kinetic energy of rapidly changing force s, shackle of the appropriate size should be used to connect otherwise theses forces will be transmitted directly to the the chain and tot eh rope. anchors. Natural fibre rope is not suitable as it is easily abraded and prone to rotting. Steel cable, although immensely strong, is expensive and heavy. Chain is extremely strong but again is heavy and is usually used in conjunction with synthetic fiber rope. Synthetic ropes of same diameter nylon and PES are considerably heavier than PP or PES. However, nylon is much stronger on a per unit weight or equivalent diameter basis than ropes fabricated from the other materials. Braided ropes are lighter than laid ropes and are generally weak. They also cost more and have few advantages other than they are easier and more pleasant to handle and do not kink. Although it can cost twice as much as PE or PP rope of equivalent strength, nylon has high extensibility and thus energy absorbing properties, an important factor in designing cage moorings. Ropes should not be attached directly to either shore or sea anchors, but instead should be connected via a section of chain. The chain serves to increase the effectiveness of the mooring system, which directly act as an efficient type of anchor and improves the holding power of existing anchor by both reducing the angle between the mooring line and anchor and by increasing energy absorbing properties of the mooring line. An alternative mooring line composed mainly of chain is occasionally employed. Typically 12-25mm chain, two or three times the maximum depth of water in length is connected from the anchor to a float positioned 10m or so from the cage and a section of rope –PES or nylonused to link the floats to the cages. The buoy minimizes the vertical loading on the cages and must be sufficiently large to support the mass of the chain in the water and to resist the vertical forces imposed by the cages on the mooring system. A single float per mooring line tends to be used, although reductions in line tension from using a series of floats with the same floatation capacity as a single float. Under shock loads, the chain/buoy acts as a spring absorbing much of the energy that would otherwise be transmitted to the anchor. Two types of mooring systems be used: multiple and single point. The former is more common and involves securing the cages in one particular orientation while with the latter the cage are moored from one point only, allowing them to move in complete circle. Single point moorings tend to be used with rigid collar designs in sheltered sites. They use less chain and cable than multiple point moorings and because they adopt a Moreover, a section of chain is necessary at the anchor position of least resistance to the prevailing wind, wave since it is much resistant than synthetic fibre rope to the and current forces, both inter cage forces and torsion prevailing high abrasion forces. There are several types of forces at linkages are reduced. Single point mooring chains are available. Wrought iron is very variable in systems also reduce the enormous net deformation seen quality; the best has excellent corrosion resistance while in conventional mooring systems and have been used the poorer grades are inferior in all respects. Mild steel with successes to moor large offshore cages. Cages chain, with low carbon and manganese contents has been moored from a single point also distributes wastes over widely recommended for cage anchorages. A fairly heavy considerably larger areas than those secured by a grade of chain is recommended. multiple point system. 35 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi The orientation of cages with multiple moorings depends one structural member to another, are frequently used. upon the nature of the site and upon the type and group Anchors are deployed to resist the principal directions of configuration of the cages. If particularly exposed or if force and sometimes may be used installed on shore as currents are strong, then it may be best to secure cages well as at sea. Mooring lines must be secured to cage in the position of least resistance to the prevailing wind collars via attachment points able to withstand the forces and current forces. Where a site is sheltered and water generated. Structural members should be used and where circulation is poor, it may be better to moor cages so that abrasion is expected the line should be protected by water exchange is maximized. However, there may be encasing in plastic pipe. restrictions on mooring orientation imposed by the site size or by suitability of mooring grounds. The number of mooring lines used determines the distribution of forces to the anchors. Most methods of mooring involve the use of ropes and chain to link the cage or cage group to anchors or pegs secured to the sea Installation methods The installation of mooring systems is an important aspect of the overall development of a cage site, and requires to be planned with care. (i) Working base: a suitable and secure area for storing bed. The mooring line is often termed as a ‘riser’. Although and laying out the mooring components needs to this is most common system there are alternatives. Some be identified – ideally a level, surfaced area. cages may use a submerged rope or cable based mooring grid, to which cages may be attached temporarily using (ii) and positioning the mooring components and near horizontal lines. One further alternative is to drive operating in the expected site conditions long posts into substrate and to attach cage directly either with ropes or with metal hoops or tyres that permit some Workboat or mooring vessel: capable of moving (iii) Cranes: dockside and on mooring vessels – capable vertical tidal and wave induced movement. In theory the of lifting and moving the mooring elements safely number and dimensions of posts required and the depth at the required horizontal reach. to which they must be buried could be computed from the estimates of the forces acting on the cage system (iv) areas, for mooring components to be taken safely and data on the soil characteristics, but in practices it is to the intended cage site. determined by experience. Although sometimes employed in sheltered and shallow inland and coastal sites with Access: – for materials to be taken to the assembly (iv) Marking out: key locations in the mooring site can suitable substrates, this method of mooring is not widely be marked out on a hydrographic chart, checked used. on site with GPS or conventional optical surveys; local transect markers can be identified, and There are a variety of methods of using single and multiple temporary positions marked with light lines and point moorings. one or two heavy ground chains can be floats laid which connects the cages to the anchors via mooring lines. Alternatively mooring lines can be run directly from (v) Making up moorings: the mooring lines and grids the cages to the anchors. Points of stress are formed need to be adjusted to length and assembled to where mooring lines are secured to the cages and so it is form the appropriate sub-components, which important that they are secured at a number of places. would then be finally linked together on site once Joints, where stress accumulate or are transferred from the anchors are laid. Primary work can most easily 36 Central Marine Fisheries Research Institute From 14 - 23 December 2009 (vi) be done on shore, using temporary measure lines Mooring maintenance or markers to help lay off the line lengths. Further Cage moorings are a dynamic system, which must respond adjustments can be done at sea, and all to motion, under load, every minute of the years it is components and connections given a final check installed. Maintenance is critical, to ensure that before installation components are physically sound and that linkages are Laying anchors and risers: if blocks are used, these can be set at the intended site, using positioning co-ordinates to define the location. For embedding anchors, these should be dropped a suitable checked periodically, bolts and shackle pins need to be tightened, and riser lines may need to be adjusted. With a rigorous and effective system of maintenance of tension) from the place of intended location, and both cages and moorings, with clearly defined parameters tensioned inwards to their final position. Laying for replacement or repair, a well designed and installed of moorings and lines should be done carefully, system should be capable of reliable and secure operation. line, to tangle or snag the line, or to endanger staff. (x) chain links, brackets, shackles, splicing eyes, need to be distance outwards (i.e., opposite the direction of taking particular care not to foul anchors with riser (ix) secure. Critical dimensions of items subject to wear – Mooring systems must be checked at regular intervals and fouling removed from buoys and mooring lines. it is Tensioning the rising lines: these need to be finally essential that any mooring inspection assesses adjusted to ensure that the cage and/or mooring component strength to see if it deviates significantly from assembly is correctly and evenly tensioned around design strength and that it should also assess likely its axes. deterioration in the interval to the next inspection. Diver swim of rising lines: finally, it is very Reference important to check the whole system visually – to ensure that blocks or anchors are cleanly placed and/or embedded, that lines are lying properly and are not kinked or tangled, and that connections are sound. Beveridge, M.C.M.B., 1996. Cage Aquaculture 2nd Edn. Fishing News Books, Oxford, p. 346. Turner R, 2000. Offshore mariculture: Mooring system design. In Muir J. (ed.), Basurco B. (ed.) Mediterranean offshore mariculture. Zaragoza: CIHEAM-IAMZ, p. 159-172. 37 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Taxonomy, identification and biology of Seabass (Lates calcarifer) Grace Mathew Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India gracejacob1985@yahoo.com Introduction female fish provides plenty of material for hatchery Lates calcarifer (Bloch), commonly known as giant sea perch production of seed. Hatchery production of seed is relatively or Asian seabass, is an economically important food fish in simple. Seabass feed well on pelleted diets, and juveniles the tropical and subtropical regions in the Asia –Pacific. are easy to wean to pellets. Seabass grow rapidly, reaching They are medium to large-sized bottom-living fishes a harvestable size (350 g – 3 kg) in six months to two years. occurring in coastal seas, estuaries and lagoons in depths between 10 and 50m. They are highly esteemed food and sport fishes taken mainly by artisanal fishermen. Because of its relatively high market value, it has become an attractive commodity of both large to small-scale aquaculture enterprises. It is important as a commercial Today Seabass is farmed throughout most of its range, with most production in Southeast Asia, generally from small coastal cage farms. Often these farms will culture a mixture of species, including Seabass, groupers (Family Serranidae, Subfamily Epinephelinae) and snappers (Family Lutjanidae). and subsistence food fish but also is a game fish. The most Australia is experiencing the development of large-scale important commercial fish of Australia, and the most seabass farms, where seabass farming is undertaken sought after game fish, generates millions of dollars per outside the tropics and recirculation production systems year in revenue for the sport fishing. Lates calcarifer, known are often used (e.g. in southern Australia and in the north- as seabass in Asia and barramundi in Australia, is a eastern United States of America). Seabass has been euryhaline member of the family Centropomidae that is introduced for aquaculture purposes to Iran, Guam, French widely distributed in the Indo-West Pacific region from the Polynesia, the United States of America (Hawaii, Arabian Gulf to China, Taiwan Province of China, Papua Massachusetts) and Israel. New Guinea and northern Australia. Aquaculture of this species commenced in the 1970s in Thailand, and rapidly spread throughout much of Southeast Asia. Among the attributes that make seabass an ideal candidate for aquaculture are: It is a relatively hardy species that tolerates crowding and has wide physiological tolerances. The high fecundity of Taxonomy Phylum Sub-phylum Class Sub-class Order Family Genus Species Chordata Vertebrata Pisces Teleostomi Percomorphi Centropomidae Lates Lates calcarifer (Bloch) 38 Central Marine Fisheries Research Institute From 14 - 23 December 2009 The above is an accepted taxonomic classification of edge of pre-operculum is with strong spine; operculum seabass or giant perch. Seabass has been placed under with a small spine and with a serrated flap above original several families by various authors in the past (e.g. the of lateral line. Dorsal fin with 7 to 9 spines and 10 to 11 grouper family, Serranidae and family Latidae, etc.) soft rays; a very deep notch almost dividing spiny from However, Centropomidae is the commonly accepted soft part of fin; pectoral fin short and rounded; several family name of this species, and the recognized generic short, strong serrations above its base; dorsal and anal name is Lates. Other names such as Perca, Pseudolates, fins both have scaly sheath. Anal fin round, with three Holocentrus, Coins, Plectropoma, Latris , and spines and 7–8 soft rays; caudal fin rounded. Scale large Pleotopomus were also given by various authors who ctenoid (rough to touch). Colour: two phases, either olive collected the fish specimens from different areas. Bloch brown above with silver sides and belly in marine (Schneider 1801) stated that Lates calcarifer occured in environment or golden brown in freshwater environment. Japan Sea but named it as Holocentrus calcarifer. In adult, it is usually blue-green or greyish above and silver English: Asian seabass, Barramundi perch; French: Brochet de mer. below. Fins are blackish or dusky brown. Juveniles have mottled pattern of brown with three white stripes on head and nape, and white blotches irregularly placed on back. The common local names of this species are listed below: Eyes are bright pink, glowing at night. English : Giant perch, white seabass, silver seaperch, giant perch, palmer, cock-up seabass Distribution India : Begti, bekti, dangara, voliji, fitadar, todah East Bengal : Kora, baor Sri Lanka : Modha koliya, keduwa areas of the Western and Central Pacific and Indian Thailand : Pla kapong kao, pla kapong Ocean, between longitude 50°E - 160°W latitude 24°N – Malaysia : Saikap, kakap 25°S (Fig. 1). It occurs throughout the northern part of North Borneo : Ikan, salung-sung Asia, southward to Queensland (Australia), westward to Vietnam : Ca-chem, cavuot East Africa. Found in coastal waters, estuaries and Kampuchea : Tvey spong lagoons. Usually occurs at depths of 10 to 40m. Philippines : Kakap, apahap, bulgan, salongsong, katuyot, matang pusa Indonesia : Kakap, pelak, petcham, telap : Barramundi Geographic distribution Seabass is widely distributed in tropical and sub-tropical Australia and Papua New Guinea Morphology and distinctive characters \Body elongated, compressed, with deep caudal peduncle. Body large, elongate and stout, with pronounced concave dorsal profile in head and a prominent snout; concave dorsal profile becoming convex in front of dorsal fin. Mouth is large, slightly oblique, upper jaw reaching to behind eye; teeth villiform, no canine teeth present. Lower Fig. 1 Geographic distribution of Lates calcarifer (FAO, 1974) 39 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Ecological distribution been recorded in the Indo-Australian region (Weber and Seabass is a euryhaline and catadromous species; inhabit Beaufort 1936). freshwater, brackish and marine habitats including streams, lakes, billabongs, estuaries and coastal waters. Sexually mature fish are found in the river mouths, lakes or lagoons where the salinity and depth range between 30–32 ppt and 10–15m, respectively. The newly-hatched larvae (15–20 days old or 0.4–0.7cm) are distributed along the coastline of brackishwater estuaries while the 1-cm size larvae can be found in freshwater bodies e.g. rice fields, lakes, etc. (Bhatia and Kungvankij, 1971). Under natural condition, seabass grows in fresh water and migrates to more saline water for spawning. Adults and Eggs are pelagic, hatch within 24 hours, and the larvae grow quickly as they move into mangrove areas, mudflats, and floodplain lagoons. Juveniles move into coastal waters after one year, and then migrate upstream where adults reside for three to four years. Populations landlocked by dams migrate to the dam face, but do not spawn. It is reared extensively by aquaculture as food or for game fishstocking programs. Catadromous migration is observed, where the fish migrates downstream to shallow mudflats in estuaries during the wet season. juveniles tend to be solitary, patrol home ranges near structure, and may be territorial. Migration is seasonal. Life history Seabass spends most of its growing period (2–3 years) in freshwater bodies such as rivers and lakes which are connected to the sea. It has a rapid growth rate, often attaining a size of 3–5 kg within 2–3 years. Adult fish (3–4 years) migrate towards the mouth of the river from inland waters into the sea where the salinity ranges between 30–32 ppt for gonadal maturation and subsequent spawning. The fish spawns according to the lunar cycle (usually at the onset of the new moon or the Fig. 2 Migration pattern of Lates calcarifer Bloch Feeding habits full moon) during late evening (1800–2000 hours) usually Seabass or barramundi are opportunistic predators; in synchrony with the incoming tide. This allows the eggs crustaceans and fish predominate in the diet of adults. and the hatchlings to drift into estuaries. Here, larval Although the adult seabass is regarded as a voracious development takes place after which they migrate further carnivore, juveniles are omnivores. The fish is skilled at upstream to grow. At present, it is not known whether stalking or ambushing prey. Analysis of stomach content the spent fish migrates upstream or spends the rest of its of wild specimens (1–10 cm) show that about 20% life in the marine environment. consists plankton, primarily diatom and algae and the rest are made up to small shrimp, fish, etc. (Kungvankij 1971). Smith (1965) noted that some fish spend their whole life Fish of more than 20 cm, the stomach content consists in freshwater environment where they grow to a length of 100% animal prey: 70% crustaceans (such as shrimp of 65 cm and with 19.8 kg body weight. The gonads of and small crab) and 30% small fishes. The fish species such fish are usually undeveloped. In the marine found in the guts at this stage are mainly slipmouths or environment, seabass attaining a length of 1.7 m have pony fish (Leiognatus sp.) and mullets (Mugil sp). 40 Central Marine Fisheries Research Institute From 14 - 23 December 2009 February to March. Spawning seasonality varies within Sex determination Identification of the sexes is difficult except during the spawning season. There are some dimorphic characters that are indicative of sex (Fig. 3). the range of this species. Barramundi in northern Australia spawn between September and March, with latitudinal variation in spawning season, presumably in response to varying water temperatures. In the Philippines barramundi Snout of the male fish can be slightly curved while spawn from late June to late October, while in Thailand that of the female is straight. spawning is associated with the monsoon season, with z The male has a more slender body than the female. two peaks during the northeast monsoon (August – z Weight of the female is heavier than males of the same z October) and the southwest monsoon (February – June). size. z The scales near the cloaca of the males are thicker than the female during the spawning season. z During the spawning season, abdomen of the female is relatively more bulging than the males. Sexual maturity In the early life stages (1.5–2.5 kg body weight) majority of the seabass appear to be male but when they attain a body weight of 4–6 kg majority become female. After culture period of 3–4 years, however, in the same age group of seabass both sexes can be found and identified as mentioned above. In a fully mature female, the diameter of the oocysts usually ranges from 0.4 to 0.5 mm. Fig. 3 Photograph of adult male and female seabass Spawning occurs near river mouths, in the lower reaches of estuaries, or around coastal headlands. Barramundi spawn after the full and new moons during the spawning season, and spawning activity is usually associated with incoming tides that apparently assist transport of eggs Fecundity and spawning and larvae into the estuary. Females are larger than males, are highly fecund, and may Seabass being highly fecund; a single female (120 cm TL) be courted by one or more males at the same time. The may produce 30–40 million eggs. Consequently, only fecundity of seabass is related to the size and weight of small numbers of broodstock are necessary to provide the fish Spawning occurs between September and March, adequate numbers of larvae for large-scale hatchery with peaks in November to December and again in production. Table 1 Relationship between size of fish and number of eggs from the gonads of seabass (Lates calcarifer Bloch) (After Wongsomnuk and Maneewongsa, 1976) Total length(cm) Weight No. of fish Range 70 – 75 76 – 80 81 – 85 86 – 90 91 – 95 5.5 8.1 9.1 10.5 11.0 3 5 4 3 3 Fecundity (million eggs) Average 2.7 – 3.3 2.1 – 3.8 5.8 – 8.1 7.9 – 8.3 4.8 – 7.1 3.1 3.2 7.2 8.1 5.9 41 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Based on studies of spawning activity under tank years of age (60–70 cm TL) when they reach sexual conditions, mature male and female fish separate from maturity as males, and then move downstream during the school and cease feeding about a week prior to the breeding season to participate in spawning. spawning. As the female attains full maturity, there is an increase in play activity with the male. The ripe male and female, then swim together more frequently near the water surface, as spawning time approaches. The fish spawns repeatedly in batches for 7 days. Spawning occurs during late evening (1800- 2200 hours). Embryonic development First cleavage occurs 35 minutes after fertilization. Cell division continues every 15 to 25 minutes and the egg develop to the multi-celled stage within 3 hours. Its development passes through the usual stages: blastula, gastrula, neurola and embryonic stages. Embryonic hear starts to function in about 15 hours and hatching takes place about 18 hours after fertilization at temperatures of 28–30°C and salinities of 30–32 ppt (Table 2, Fig Because they are euryhaline, they can be cultured in a range of salinities, from fresh to seawater. When they are six–eight years old (85–100 cm TL), seabass change sex to female and remain female for the rest of their lives. Sex change in Asian populations of this species is less well defined and primary females are common. Although seabass have been recorded as undertaking extensive movements between river systems, most of them remain in their original river system and move only short distances. This limited exchange of individuals between river systems is one factor that has contributed to the development of genetically distinct groups of barramundi in northern Australia, where there are six recognised genetic. 4a & b). Larvae Table 2 Embryonic development of seabass eggs (Kungvankij 1981). Newly-hatched larvae have total length ranging from 1.21 Embryonic stage to 1.65 mm averaging 1.49 mm. The average yolk sac length is 0.86 mm. One oil globule is located at the anterior part of the yolk sac which causes the hatchling to float almost vertically or about 45° from its usual horizontal position. Initial pigmentation is not uniform; the eyes, digestive tract, cloaca and caudal fin are transparent. Three days after hatching, most of the yolk sac is absorbed and the oil globule diminishes to a negligible size. At this stage, the mouth opens and the Hours & minutes after spawning Hours Minutes Fertilization - 5 2-cell - 35 4-cell - 55 8-cell 1 10 16-cell 1 30 32-cell 1 50 64-cell 2 20 122-cell 3 - Blastula stage 5 3 jaw begins to move as the larva starts to feed. Gastrula stage 7 00 Larvae recruit into estuarine nursery swamps where they Neurola stage 9 10 remain for several months before they move out into the Embryonic stage 11 50 freshwater reaches of coastal rivers and creeks. Juveniles Heart functioning 15 30 remain in freshwater habitats until they are three–four Hatch out 18 - 42 Central Marine Fisheries Research Institute From 14 - 23 December 2009 There are at least two pigmentation stages in seabass larvae. At 10–12 days after hatching, the pigmentation of larvae appears dark gray or black. The second stage occurs between 25–30 days old where the larvae develop into fry. In this stage, the pigmentation changes to a silvery-coloration. It has been observed that only healthy fry of this stage (20–30 days) swim actively. They are always lighter in color. Unhealthy post larvae have dark or black body coloration. Growth The growth rate of seabass follows the normal sigmoid curve. It is slow during the initial stages but becomes more rapid when the fish attains 20–30 gm (Table 3). Fig 4a Development of egg It slows down again when the fish is about 4 kg in weight. Table 3 Age, average body length and weight of seabass under tank conditions Age(days) Average length(mm) Average body weight Fertilized eggs 0.91 0 1.49 1 2.20 7 3.61 14 4.35 20 9.45 30 13.12 0.1 40 17.36 0.5 50 28.92 Conservation status Not listed by the IUCN, but has been threatened by Fig 4b Development of egg habitat destruction and over fishing. 43 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Nursery rearing of seabass fry and importance of grading and seed transportation Shoji Joseph Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India sjben@yahoo.com The Asian seabass (Lates calcarifer) is an important food that affect the survival rate of seabass larvae as well as fish and a potential aquaculture species in tropical juveniles. In case of inadequate feeding times not only countries. It exhibits catadromous habits within its areas the lack of food but also the cannibalism will work of distribution. It is an advantageous culture species together and the survival rate will be lower in double because after early larval rearing in seawater, it can be effects. The larvae or juveniles cannot survive if there is cultured in all levels of salinity, from fresh to seawater, inadequate supply of food, which comprises various live and in a variety of culture systems from open ponds and organisms, and that again varies with the development cages to flow-through and closed recirculation systems. of the larvae. Most of the food that seabass larvae feed In addition, this species produces large number of eggs on is composed of live zooplankton. The larvae first begin that can be reared intensively on fresh and pelleted feeds, to feed on rotifer. It is reported that other kinds of food and can reach a market size of 350 to 700 g in one year or have also been tried with the early larvae but without less periods under optimum culture conditions. success. The supply of live zooplankton is expensive and Seabass spawn naturally in captivity and the fertilized eggs take 12 to 15 hours for hatching. The spherical eggs range from 0.74 to 0.80 cm in diameter with a single oil globule from 0.20–0.28 mm in diameter (Maneewong and Watanabe, 1984). The mouth opens when the larvae get to about three days old and the yolk has been almost completely absorbed. This is a sign that the fry can start to feed. Seabass larvae and juveniles sometimes causes problems because zooplankton culture needs time, facilities and skills. Further, the different kinds of live food required must be prepared in time to satisfy the need of the fast-growing larvae. To maintain a high survival rate, the feeding schedule for the larvae must be closely adhered to. Nursery Management Tank Seabass fry and fingerlings should be reared in concrete Seabass is a carnivorous voracious feeder; and it is highly tanks up to the size 2.5 cm or 1 inch. After that, they can cannibalistic in the earlier stages like larvae and juveniles. be transferred for rearing in nylon net cages until they Food and feeding are two of the most important factors attain 25 cm or 10 inches in about 2 to 3 months of culture 44 Central Marine Fisheries Research Institute From 14 - 23 December 2009 period. The rearing tank should be cleaned up every time (iii) the replacement may be gradual, occurring over several before using. The rates of water replacement in the rearing days, as in the culture of red sea bream and Japanese tanks depend on feeding period of each age stage. In the flounder. On 25th day, when the fry measures @1.0 cm, it period of rotifer feeding to prevent the loss of rotifer should be transferred to nursery tanks in the hatchery or through the outlet, approximately 10–20 percent of the nursery hapas at the farm site for weaning. Though seabass water in the rearing tank is drained out only for the prefers live fish food it could be weaned to trash fish within replacement of rotifer supply each day. During Artemia 5-7 days. Fry are stocked @ 1000 nos./m3 in 4-5 tonne feeding period, approximately 50 percent of water is capacity tanks. The cooked and minced fish meat, made changed while almost complete change is made during into small pieces of 1.5- 2.5 mm, should be given as feed trash fish feeding period. The sediment of dead organisms, ad libitum during the nursery rearing. Grading (removal of larvae or leftover food is siphoned out everyday. The shooter fish) should be done on alternative days to reduce management of seabass nursery is shown in Fig.1. cannibalism. 1.__________3.__________10.__________14.__________20.__________25.__________30.__________40 2.__green water and other algae__ _________Rotifer _______ ___________________Artemia_______ ______Daphnia__________ _______Trash fish_________ 3.——RCW——10-20% change———I————————50%——————————I——80%————— 4. ___________1st grading____I_________2nd grading___I______Weeky once_______ Fig. 1. Management method for seabass nursery tank within the first 40-day period 1 Time duration 2 Feed 3 Water change 4 Grading. Weaning Importance of grading and grading techniques The inclusion of artificial food in the diet of marine fish Cannibalistic behaviour of seabass fry can be observed larvae is a critical stage in intensive larval rearing. The after the fry completes metamorphosis, when they are process of changing diet of the fish larvae from the live about 15 days old (15 mm in total length). To maintain a feeds to the artificial diets or vise versa is called weaning. uniform size and minimize the mortality of the fry, grading Weaning reduces the dependence on live feeds, and of fry to size groups at regular and frequent intervals must therefore reduces hatchery running costs. Person-Le Ruyet be done. Due to cannibalistic nature of the fish, size (1991) described three weaning strategies which have been selection or grading or sorting of the larvae is of prime applied to different species of marine fish larvae, with importance based on the size of the fish. The first sorting different levels of success; (i) weaning at first feeding has should start at the second week since during this period; been achieved with plaice and sole with lower survival than the bigger fish can eat the smaller ones. After the first achieved with live feeds; (ii) larvae may be reared for some size grading at around 12-15 days old, size grading should time on live feed, which is then replaced abruptly with be done every 3-5 days (Maneswongsa, 1986; Ruangpanit, artificial feed; this strategy is used for European seabass or 1988). The easiest way of sorting is to use screen with 45 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi various mesh size so that the various sizes of fish can be the water bodies. The net cages usually uses are 2x1x1.5 separated easily. Another material usually used for grading m and they are usually set in open waters one day before consists of plastic containers punched at the bottom with stocking to remove the contaminants if any. Stock of holes of 2, 3.5, 5, 6 and 7 mm in diameter. Fish are placed 2,000–3,000 fry are raised to the fingerling size in these in the plastic containers which are floated in the newly cages. prepared larvae nursing tank. The small fish can pass through the hole to the new tank. The remaining fish in Survival Rate the plastic containers are transferred into another tank The system of culture outlined above gives about 85 and likewise graded with the use of a plastic container percent hatching rate and a survival rate of 1–7 days old with larger holes. Different types of graders fixed as well larvae of 30 percent. For 8–15 days old larvae the survival as adjustable types are now available in the international is 80 percent, after which they can be maintained market and a few types in the Indian markets. indefinitely with negligible mortality (Table 1). Stocking same size fish will reduce the rate of cannibalism, Table 1 Survival rates of seabass larvae at various ages under normal stocking rates in tanks thus the survival rate can be increased and the growth rate of the fish could also be faster and more uniform. Age (days) No. of larvae* per liter Survival Rate(%) 1–7 30–40 37.2 voracious carnivorous feeders and the competition for 8–15 15–20 80.9 16–23 5–10 70.0 food is very high during the feeding time. If the number 24–30 2–5 85.3 Grading is also important in the fact that these fishes are of fishes in the tanks as well as in the hapa are high, the competition again increases and only the fittest will get the food. Again these are column feeder and usually they * Normal stocking density used in nursery tanks. Salinity acclimatization never feed on the left over food in the bottom. So all of It is a euryhaline species except in its early larval stages. them will have to get the food and eat in the same time, These can be easily acclimatized from one salinity to any this will not be possible in the tanks or hapa. Here the other salinity i.e. from sea water to fresh water within weak ones cannot grasp food as efficient as the healthier short period of time without any mortality. Thus, it is an ones and hence they become more weak when compared advantageous culture as it can be cultured in all levels of to the eating ones that grow further in size. salinity, from fresh water to sea water, and in a variety of culture systems from open ponds and cages to flow- Growth and care of larvae as they develop to fry and through and closed recirculation systems. It can easily Juveniles adjust to change of 5 – 10 ppm at a time. Therefore in a When the fry are 50 days old or 1.0-2.0 cm length they day it can be changed from sea water to fresh water and are transferred to another tank (Ruangpanit et al., 1988). vise versa. The ground fish meat can be fed at age 45 days with Artemia nauplii. Filtered sea water is totally changed and Collection and conditioning of fry before transport supplied every day. The semi moist compound diet is given Fry are collected from the rearing tanks and placed in three times a day. The juveniles can also rear in the net smaller receptacles. Fry are treated with 5 ppm of cages in the open waters. They can be moved from the acriflavine solution or 0.5 ppm of copper sulfate solution rearing tanks for culture in net cages of different size and for 5–10 minutes. There should be no feeding within 1–2 shape according to the convenience and availability of hours before packing. 46 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Packing is advantageous than other methods since it can be easily Plastic bags of 40 × 60 cm of proper gauge are filled with 6–7 litres of fresh seawater and saturated with oxygen; 10–12 litres of oxygen gas are used for packing. The amount of transportable fry depends on size of fry, water temperature in plastic bags and duration of travel and handling from source of fry to its destination. managed and installation of rearing facility requires less space and capital investment. The infrastructural facilities including the man power is very less compared to the tank systems. The huge amount of water exchange can be avoided if it is reared in hapa in the ponds. It is easy to maintain the water quality parameters in the ponds if it is having easy approach to the natural water bodies. If Transport the ponds are provided with the water exchange facility In transporting by truck, a mixture of crushed ice and it is well and good. The ponds with tidal fled systems are sawdust is needed to control the water temperature in very good as the water can be entered and removed easily the plastic bags during transport. The mixture is spread without any power consumption. Again the number of uniformly on the floor of the truck before the plastic bags the hapa can be extended to any scale depending on the are laid upon it. The proportion of crushed ice and sawdust necessity and the capability of the farmer. It can be is 1:1 for long—period transport (12–16 hours) and 1:2 for maintained in a corner of the grow-out pond or near the short periods (4–5 hours). Transportation should be carried grow-out cages itself. The water flow in the cage site out at night time. By this method, it is possible to control washes away the metabolites and excess uneaten feed. the water temperature between 19–23° C. Pond preparation The pond is made ready three weeks ahead of the date on which the fry is expected. Adequate provision of water inlet and outlet should be provided. A slope towards the drainage side is preferred for the easy removal of the waste materials for keeping good water quality in and around the hapa. Both sluices/ the inlet and outlet channels should be guarded by 1 mm mesh nets to prevent the entry of unwanted fishes as well as escape of the fry in the case of some hapa damage. The nursery pond should be free from predators. Predators are killed by mahua Fig. 2 shows the observed fluctuation in temperature of the water in the plastic bags during transport. It was also observed that the dissolved oxygen starting initially at 5.3 to 5.0 ppm will drop to 2.3-2.6 ppm at destination. Pond nursery oilcake (which is toxic for three weeks), which then acts as a good fertilizer, giving a rich crop of zooplankton which is good for the juveniles in rearing ponds. If there are no weeds, to kill predators and competitors quickly, just add 100 kg of urea followed 24 hours later by 200 kg of fresh Nursery rearing of seabass fry in ponds in hapa to the size bleaching powder (which is toxic for only a week) for a 1- of stocking is essential before release into the cages. ha area of a 1-m deep pond. Fish killed in this way is Nursery ponds may range in size from 500-2000 m . A edible. A week after treatment with bleaching powder, water depth of 1-1.5 m is desirable. Rearing of juveniles add fresh cow dung (2,500 kg/ha) or a mixture of cow in hapa in the earthen ponds is easy and economical when dung (2,500 kg/ha) and poultry manure (1,250 kg/ha). If it compared with that of the tank systems. This method mahua oilcake is used, fertilizer need not be added for 2 47 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi the first 15 days. The pond should be stocked as soon as The mesh size as well as the size of the hapa can be it is ready and as early in the season as possible to get changed as the fishes grow to bigger sizes which will fry, which makes the best use of the available water and increase the growth and at the same time reduces the the high temperatures. clogging and the cleaning due to it. This would allow In prepared nursery ponds, fry of 2.5 to 4.0 cm size can be stocked @ 1500-2000 nos/hapa of 2 x 2 x 1 m. The most convenient cage design is a rectangular cage made of synthetic netting attached to wooden, GI pipe or bamboo frames. It is either a) kept afloat by styrofoam, plastic carbuoy or b) stationary by fastening to a wooden or bamboo pole at each corner. The size of cage varies from 0.9 × 2.0 m and a depth of 0.9 m to 1.0 × 2.0 meters and a depth of 1.0 meter (Figure 1). The mesh size of the nylon net is 1.0 mm. The mesh size of the hapa should be appropriate with the size of the fishes as well as it should allow the water movement. Water exchange to the extent of 30% is required daily to the pond. Fry must be fed with supplementary feed of chopped and ground fish (4-6 mm size) @ 100% of the water to pass through the cages more freely. Nursery cage size may range from 3 m (3x1x1 m) to 10 m (5 x 2 x 1 m) with a mesh size of 10 mm. Cages/ hapa should be checked and cleaned regularly. The fry on reaching a size of 25 -40 g at the end of another rearing period of 30-45 days can be stocked in the open sea cages for the grow-out system. Usually a survival rate ranging from 50-70% could be obtained. The net cage should be checked daily to ensure that it is not damaged by crabs or clogged with fouling organisms. The cage should be cleaned every other day by soft brushing in order to allow water circulation in the cage.The survival rate for the nursery period would be 50 to 80 percent. This would depend on feeding, aquatic environmental conditions, and the expertise of the fish farmers. body weight, thrice a day, in the first week. The feeding Trash fish is the main feed for seabass culture. Trash rate is gradually reduced to 60% and 40% during second fish should be fresh and clean. Trash fish used are and third week respectively. The minced fish meat, made sardines and other small marine fish. The trash fish into small pieces of 1.5-2.5 mm, should be given as feed should be chopped and fed thrice a day, in the early ad libitum during the nursery rearing. Grading (removal morning, afternoon and evening. The size must be of shooter fish) should be done on alternative days to suitable for the size of the mouth of the fish. The farmers reduce cannibalism. At this stage the nets of the hapa should give the feed slowly and watch the fish. Feeding should be cleaned for 3 – 4 days as it gets clogged with should be stopped when the fish no longer come up to algal materials which reduces the water flow and the the surface; it shows that the amount of feed is enough water quality within the hapa. The expected survival for them. rate would be 80-86% with an average size of 5 to 7.5g in 30-35 days of rearing in the hapa. However, after a Diseases month of nursing, they can be transferred to cages with If hygienic conditions are maintained, the juveniles are nylon net with mesh size of 0.5 cm. Stocking is done generally resistant to diseases. However, since the larvae separately for each size group. This would minimize the are stocked in the tank for a long period, sometimes losses from cannibalism. Fingerlings of 2.5–5.0 cms they show their abnormal swimming character, stop should be fed with ground trash fish at 8–10 percent of feeding, and turn black. These are signs of disease or body weight daily or about 4 to 5 times a day. After that, poor health so that if these occur, they should be treated they can be fed with finely chopped trash fish. with 1:2,000 parts formalin solution for 10–15 minutes 48 Central Marine Fisheries Research Institute From 14 - 23 December 2009 for 2–3 days continuously. It is commonly known that Collection, conditioning and transport of juveniles to the the seabass fry when collected from natural areas are grow-out systems big enough so that they can be suitable for stocking grow Fry are collected from the rearing tanks and placed in out ponds and cages. As now it is able to spawn the fiber glass tanks in the same salinity. There should be no fish and grow the larvae and juveniles under controlled feeding within 1–2 hours before packing. If the salinity conditions, better knowledge is available on their growth. of grow out is different the fishes should be acclimatized It is also successfully completed the nursing of the to the salinity of grow-out first before transportation. As seabass larvae and juveniles in controlled conditions with the fishes are now grown to a bigger size, it is better to relatively high survival rates without much health transport them in the bigger containers like syntax tanks problems at present. with aeration in good quality waters. 49 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Important management measures in cage culture Imelda Joseph Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India imeldajoseph@gmail.com To get the maximum benefit out of the cultured system, handling, loading and transport are highly stressful to fish, given the restrictions imposed by the site, species or type resulting not only in physical damage, but also in changes of feed used, the stock must be kept in conditions which in blood chemistry, increased oxygen consumption, minimise losses and promote good growth and finally osmoregulatory problems, and increased susceptibility to optimum production. It is to be considered first that the disease. Under stressful conditions, fish must expend cages must be of a reasonable size that makes more energy to maintain homeostasis (tendency of an management by an individual or small group easy. organism or cell to maintain internal equilibrium by The major factors to be taken care in cage management are: z z z different from terrestrial animals: they are immersed in their environment and cannot go somewhere else. Some appropriate to the site and rearing conditions disease agents are almost always present in the water Feeding the fish in the most cost effective manner (ubiquitous). These opportunistic pathogens will invade aimed at maximum production fish when they become stressed. Thus, it is essential to Ensuring the best possible water quality within the Maintaining cages, moorings, anchors, nets and related accessories z combat disease. Aquatic organisms are fundamentally Stocking the candidate species at optimum density cages z adjusting its physiological processes) and less energy to reduce stress factors in cultured fish. Common measures to reduce stress are: a) Starvation before handling of fish: Handling is a source of stress as it puts fish under extreme conditions like Regular monitoring of the cultured species by overcrowding. Starving the fish for 24 - 48 h (to clean sampling, for details on health conditions, removal of their gut of food and to reduce O2 consumption) prior dead fishes, and treatment of infected fish Stress reduction to the fish to handling will reduce stress and will avoid the deterioration of water quality when fish are overcrowded. Seabass, Lates calcarifer, however, Stress can be defined as any physical, chemical or require only 1-2 h starvation prior to packing. Because environmental stimulus which tends to disrupt normal of rigours of journey fish should be carefully checked well being of an animal. The processes of capture, and injured or weak fish should be removed. 50 Central Marine Fisheries Research Institute From 14 - 23 December 2009 b) Sedation during handling and transportation: In transport fish during night or packing containers with situations such as handling or transportation, fish are ice and saw dust (1:1). If fish have to be transported overcrowded. Therefore, there is a higher risk of skin over considerable distances there is also a risk of a injuries (scale removal, abrasion etc.). To avoid such build up of toxic metabolites, such as CO 2 and damages, sedation using approved fish anaesthetics/ ammonia and increased bacterial load. sedatives is recommended as it decreases the level of stress and possible skin injuries. g) Lowering metabolic rate and thus oxygen consumption and waste production : Through a c) Grading of fish to give a homogeneous population: combination of light sedation and hypothermia When size variation increases in a cage, it often creates lowering of metabolic rate and thus oxygen competition between the larger and the smaller fish. consumption and waste production can be achieved. This can result in stress, especially for the smaller fish. Absorption of ammonia and CO 2 and control of In addition, when feeding, the bigger fish are stronger bacterial growth through the addition of natural and get more feed. As a consequence, the smaller fish zeolite, a buffer and an antibiotic to the transport get weaker and more susceptible to disease. As they media is also practiced (only after standardization). get sick, they will also become a source of infection for bigger fish as size variation is also a source of Good records of water quality conditions, growth and cannibalism (leading to horizontal disease mortalities should be kept so that management transmission). For seabass, grading is essential during procedures can be properly evaluated and modified as and the initial stage of growth due to its cannibalistic when necessary. behaviour Seed supply and stocking d) Good water quality maintenance: Water quality should be monitored on a regular basis and be maintained at optimal conditions. Any species for which seed is readily available is ideal for cage aquaculture. Those fro which hatchery technology is standardized is ideally suited for cage culture. Wild e) Over-feeding to be avoided: Since over-feeding can collected seed can also be used for cage culture if induce stress and unconsumed feed will pollute the adequate number is available in healthy condition. Nursery water, it should be avoided. rearing is very crucial for all species and specially seabass, Transportation process: Plastic bags filled with one f) third with water and the remaining space filled with oxygen prior to sealing and double bagging for safety is better for less than 4cm fry of seabass. Insulated (with thermocol/ saw dust etc.) transport box (1t to with frequent grading and adequate feeding. For seabass, if grading is not done periodically, cannibalism will considerably reduce the stock volume. However, a 30 percent loss in stock is anticipated in normal case during nursery rearing of fry to cage stocking size (20-30 g). 3t) mounted on truck can also be used for fish Before stocking the fish to cages, care should be taken to transportation. The tanks should have smooth (round) ensure that the temperature of the fish is adjusted to corners to minimize damage to the fish, and are often approximately that of their new environment. It is better provided with aeration facility during transport. if transfer is done during evening or early morning hours. Transport problems may be aggravated by high When transported using tanks, the volume of water is temperatures and by salinity. Therefore, it is better to reduced prior to the fish being transferred by hand or net. 51 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi If nets are used, these should be of fine knotless mesh to z High wastage, which affects water quality minimize damage. Feeding of fish on transfer to the cage z Increased bacterial load in raw diet which may lead to can commence 3-4 h after transfer. bacterial infection. Feed management Dry diet are less polluting, stable in water, nutritionally Feed and the feeding regimes need proper management complete, easy to transport and store, available in floating for better health and growth of the cultured stock. and sinking forms, etc. however, they are expensive and However, the quality and safety of feed and the use of formulation not known and cost escalates from one fish medicines and chemicals must be controlled by operation to the next depending on demand. concerned agencies so that it will integrate aquatic product security examination, environmental monitoring and fish disease prophylactic systems at different levels. Feeds and feeding Storage of feeds Storage facilities are essential for cage fish farming operations. Feed bags should be stored without open access to moisture and thus to prevent fungal attack. Feeding is essential in cage farming especially if stocking Trash fish may arrive at the farm in either frozen or rate is towards the higher side or to the maximum carrying unfrozen state and since fish spoils rapidly it should be capacity. As in other aquaculture operations, the feeding checked for freshness before being stored. Smell and cost accounts for an estimated 40-60% in cage farms appearance should be sufficient indicators of quality. Cold also. Formulated feed meeting with the complete storage is ideal for trash fish. nutritional requirement of carnivorous fish is used in many parts of the world for such species. However, the cost is high for such feeds. Fresh or frozen minced and chopped trash fish still forms the main stay feed for a number of Shelf life of various feeds Feed type Storage and duration Dry feeds (Rice bran, wheat middling) With < 10% moisture content and stored in cool , dry and pest free environment; can be stored for several months Trash fish frozen feed with high fat content up to three months at – 20°C; low fat content more than one year a t– 20°C Pellet feeds 2-3 months carnivore groups cultured. Economic factors and problems with diet formulation, feed storage and distribution are the principle reasons why this type of feed remains popular in some quarters. The advantages of using trash fish are: z Cost effective z Availability (of the 3mt in India @ 40 % is trash and Feeding used in chicken and swine feed. Why not fish feed to Feeding should be done throughout the culture period at fish rather than to poultry and livestock?) varying levels depending on the growth rate and natural feed availability. Hand feeding is done in most cases and is The problems in using trash fish are: z Seasonal Fluctuation in flesh quality z High moisture content and expensive to transport recommended for small scale farmers. However, mechanical feeders are used in large scale cage farms – demand feeders and automatic feeders are the two types of feeders used. (best for farming operations sited close to fish landing Feeding rings can be used if floating pellets are used. Feed or processing centres). trays set inside the cage at different positions can also 52 Central Marine Fisheries Research Institute From 14 - 23 December 2009 be used for feed distribution. By hand feeding, the feeding of fish can be watched and can be fed till satisfaction. While doing so, the stocks health status can also be monitored (stressed or sick fish stops feeding first). Frozen trash fish is thawed first, chopped and minced and broadcasted over the surface using a shovel or scoop. Water quality management pH, ammonia and turbidity The desirable range of early morning pH for fish production is from 6.5 to 9. Both ammonia and nitrite are toxic to fish. The level of ammonia toxicity depends on the species of fish, water temperature, and pH. A healthy phytoplankton bloom (green water) is one with a Secchi disc visibility of 15 to 24 inches and clarity above 24 inches indicates poor phytoplankton productivity. Visibility of less Water quality management is a key ingredient in a than 12 inches indicates a plankton bloom which is too successful fish culture practice. Most periods of poor dense and may cause low dissolved oxygen problems. growth, disease and parasite outbreaks, and fish kills can Visibility of less than 6 inches is critical for fish. be traced to water quality problems. Water quality management is undoubtedly one of the most difficult Routine Management problems facing the fish farmer. Water quality problems Water quality monitoring are even more difficult to predict and to manage Oxygen Monitoring of water quality is essential z To avoid losses caused by lethal changes in water quality In cage culture situations, if proper water exchange is not there, low dissolved oxygen is particularly acute because z To evaluate site and configuration of cage the fish are crowded into such small areas. Most fish kills, z To maintain optimum stocking and feeding requirements disease outbreaks, and poor growth in cage situations are directly or indirectly due to low dissolved oxygen. Dissolved z oxygen management is one of the most critical management techniques that must be learned by a fish farmer. The cage net mesh should be kept open always to have maximum flow of water and no drifting objects or plants should obstruct water flow in the cage system. To evaluate the general condition of stock, so that if stressed, can avoid handling. z To gain information of long term changes in water quality at a site so that variation in production may be properly evaluated. Data on dissolved oxygen and temperature are essentially Temperature collected. Measurements to be taken preferably at early Temperature is critical in growth, reproduction and morning hours and mid-day, and readings of both inside sometimes survival. Each species of fish has an optimum and outside cages and at cage surface and bottom should temperature range for growth, as well as upper and lower be made. lethal temperatures. Below the optimum temperature Data on nitrogen (ammonia, nitrite and nitrate) and feed consumption and feed conversion decline until a dissolved phosphorus, pH, turbidity etc. will give a clean temperature is reached at which growth ceases and feed idea about the cage environment. consumption is limited to a maintenance ration. Below this temperature is a lower lethal temperature at which Waste control and effluent management death occurs. Above the optimum temperature feed Cage-farm wastes are usually in the form of uneaten feed consumption increases while feed conversion declines and fish faeces. Feed is usually the major input to the 53 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi cage-farm operations. Feeding should be scheduled in surroundings (where pathogens can be found). However, such a way to ensure that feed wastage is kept to a it is necessary to reduce the risk of contamination by minimum. Many operators now use extruded fish feed of simple management practices aimed at reducing the improved digestibility to maximize assimilation and pathogen pressure in the environment. Such practices minimise loss to the environment. Use of floating feed is include proper system maintenance by removing excess vital for cage-farm operations. Mooring cages in deep suspended particles and uneaten food which is a potential waters, leaving 3-5 m bottom space and where good substrate for pathogens. Moreover, their presence reduces current flow results in cage wastes being easily flushed water flow and therefore the available dissolved oxygen away, thereby avoiding organic build up under the cages. for the fish. The frequency of net cleaning depends on Health management practices the severity of the fouling. The removal of dead or moribund fish on a daily basis is an important sanitary The objective of health management is to maintain a good measure, as well as important for record keeping. Dead health status, assuring optimum productivity and the fish, especially in tropical water, decay quickly and can avoidance of diseases. In aquaculture, the economic risk be a critical source of horizontal disease transmission as associated with diseases is high. It represents a potential the remaining live fish will tend to eat the dead fish. loss in production through mortality and morbidity, and might decrease investor confidence. Moreover, the cost to treat diseases when they are already well established is high and treatments are often initiated too late and are therefore rarely effective. Thus, aquatic animal health management must be a global strategy that aims to prevent diseases before they occur. Selection of hatchery-raised fingerlings: The overall health status of fry and fingerlings is a critical factor for a successful production cycle. When choosing a species to be farmed, preference should be given to species that are already available from hatcheries. The attention given to fish in the hatchery, and the availability of specific larval diets required to obtain strong juveniles, will allow for a Aspects of health management practices – to improve constant supply of good quality fingerlings. Presently, the fish health and survival availability of hatchery-raised fingerlings is limited. The Responsible transportation of live aquatic animals: Increased trade of live aquatic animals and the availability of hatchery-raised fingerlings should certainly increase in the near future. introduction of new species for farming, without proper Record keeping and disease monitoring: Often, in small quarantine and risk analysis in place, result in the further scale operations, recording of farming parameters such as spread of diseases. A scientific process should be daily mortality, feed consumption, growth rate and water undertaken to assist decision making regarding the risks quality parameters is not standard. Record keeping is crucial versus the benefits for the species intended to be in understanding the epidemiology of diseases and can also imported. allow us to identify critical management points in the Hygiene, disinfection and biosecurity : Hygiene and biosecurity aims at preventing the introduction of any production cycle. The collection of this historical data will help us take early action in the case of disease outbreaks. disease agent into the farm and should limit the spread Proper disease diagnosis – a prerequisite for effective of disease. Good sanitation practices in cage-farming health management systems are difficult to implement as there are no filters As aquatic animal health management is about or barrier between the cage environment and its implementation of control measures to prevent the 54 Central Marine Fisheries Research Institute From 14 - 23 December 2009 incidence of diseases, it is a prerequisite to have a good and feeding policies and timing of harvesting. Recording understanding of diseases that might occur in a particular of mortalities is essential, as a change in incidence of fish species. Therefore, adequate attention should be given mortalities can help warn of the onset of disease outbreak to disease diagnosis and epidemiology studies. and gives the farmer valuable information in the progress of the stock and management strategies (stocking Fish husbandry and management Choosing the optimal fish density is important in cage culture. Depending on the fish species and water quality conditions (especially the oxygen saturation of the water), there is a certain fish density that should not be exceeded. A common mistake is to increase the stocking density to compensate for a decrease in survival rate. This is a source of stress for the fish that can lead to skin injuries, low performance and a higher susceptibility to disease. In contrast, stocking fish optimally will allow fish to grow to their best potential and decrease the risk of disease densities, feeding rates etc.) Harvesting of fish is done continually or in batches, depending on how the production cycle is managed. Before harvesting the fish may be starved for a day to have empty gut, which will help in shelf life of the produce. Fish can be harvested in situ or the cages towed to a convenient place where the netting operation may be carried out more smoothly. The process of harvesting is simple, where the net is lifted up and fishes are concentrated to a small volume and scooped out. outbreaks. Maintenance of cages and gear Regular monitoring of fish from disease point of view is Irrespective of the damage that can be caused by storms, also essential. Often the first signs that something is predators, drifting objects, poachers, all materials used wrong can be surmised from changes in behaviour. Farmers in construction of cages have a definitive life span and should therefore be used to observing their fish without will eventually wear out. Cages, nets and moorings unduly disturbing them, and form a general picture of how therefore must be checked at intervals for signs of damage they are disturbed and behave under normal cycle of and wear and tear and repaired or replaced if necessary, environmental conditions which occur at the site, i.e., as not only cages and stock be put at risk, through neglect, dawn/mid day/dusk, high tide/ low tide, feeding/non- but human life may also be endangered. Mooring must feeding etc. changes in feeding behaviour is an indication be checked regularly by divers, particularly after heavy of poor health. wind/storms. Mooring level should be kept free from If something wrong is observed , then some fish should fouling and worn shackles replaced. be sampled and examined further, for changes in general Cage nets may be checked during cleaning, which is done physical appearance (deformed spine), skin (colour, more frequently during cage culture. Divers may have to presence of lesions, rashes, spots or lumps, excessive go down and observe the net every week or so, during mucus), eyes (bulging eyes, cloudy lens), fin and tail favourable weather conditions. Small tears may be (erosion) are all signs that something is wrong. repaired at the site itself, while major repairs should be Fish sampling should be done regularly so that the growth done on shore only. of stock is monitored. This information with records of In marine environment fouling is a major issue and in mortalities is necessary for making a number of rotating design (single point mooring system) it is reduced. management decisions, such as determination of stocking Therefore, the nets have to be frequently changed. In any 55 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi case, nets of any particular mesh size should be exchanged Net cleaning can be done physically or by chemical quite often for ones with larger size as the fish grow. Mesh treatment. Physical cleaning involves removing and scrubbing size should be carefully selected at each stage of growth the net and drying. For chemical cleaning bleaching powder too. If too small mesh size is selected, then matter or formic acid (3%) can be used. The rate of bio-fouling on exchange is restricted and if too large, escape is possible. cage frame is much slower than on net cages, and doesn’t The frequency of net charge varies from once in a week to need more frequent cleaning. Cage frames are usually cleaned once in a year depending upon the site location, materials in situ using a hand brush both above and below the water used, season and management and design of cage. line to dislodge weed and accumulated debris. 56 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Integration of seaweed (Kappaphycus alvarezii) and pearl oyster (Pinctada fucata) along with Asian seabass (Lates calcarifer) in open sea floating cage off Andhra Pradesh coast Biswajit Dash, Suresh Kumar, M. and Syda Rao, G.* Regional Centre of Central Marine Fisheries Research Institute, Visakhapatnam, Andhra Pradesh, India *Central Marine Fisheries Research Institute, Kochi, Kerala, India dashbiswajit999@rediffmail.com Introduction Aquaculture is growing very fast and its growth is expected to continue and it is necessary to supply fish for the ever growing population of our country. In India, fish production and consumption is considered to be important and needs to be promoted. As capture fisheries have almost become stagnant, diversification of aquaculture is highly necessary. Considering the limited scope of freshwater aquaculture and the availability of vast coastline, open sea cage culture gained importance in the present day mariculture practice. Open sea floating cage culture is an alternative sustainable practice for rearing fish and shellfish species and polyculture along with seaweeds may also improve profitability and sustainability. Open sea cage culture is an aquaculture production system where high density of fish is cultured in floating cages. Floating cages are widely used in commercial aquaculture and individual cage units of the cage and to utilize this form of nitrogen and phosphorus as the source of nutrient for the cultivation of valuable sea weed, the study has been conducted to see the possibility of co-cultivating sea weed Kappaphycus alvarezii and Asian seabass Lates calcarifer in open sea floating cage in Bay of Bengal off Visakhapatnam coast in Andhra Pradesh. Cage culture is an alternative sustainable practice for rearing fish and shellfish species and polyculture along with seaweeds and pearl producing oysters may also increase production. In this experiment, at the open sea cage demonstration project site at Visakhapatnam co-cultivation of Asian seabass (Lates calcarifer), the seaweed (Kappaphycus alvarezii) and the marine pearl producing oyster (Pinctada fucata) was undertaken in the floating cage. It was carried out in an offshore area near the Visakhapatnam Regional Centre of Central Marine Fisheries Research Institute, off Andhra Pradesh coast, Bay of Bengal, India. desired shapes and sizes can be tailored to suit the needs. Basics of the integrated system The release of NO3 and PO4 from the high density of fish Integrated cage culture with sea weed, oysters and fish stock and due to heavy feeding from the nearby areas of is a method of raising animals and weeds needs a floating 57 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi cage which permits a good water exchange and waste the oysters. Proper care must be taken with regard to removal into the surrounding water. Adequate water floating system and buoyancy, a good service system for circulation is essential to make the nutrients available collars and fittings and a good mooring system and a for the growth of the sea weed. However, the following proper anchorage to hold the cage. A mooring system criteria need to be given attention. must be powerful enough to resist the worst possible Site selection combination of the forces of currents, wind and waves without moving or breaking up. Appropriate site selection is important for successful enclosure aquaculture. Sheltered, weed-free, shallow bays Cage positioning (6-10 m deep) are the ideal locations for installing cages. Positioning of the cage for good growth of fish and weed The sites should have adequate circulation of water, with should be done in open areas with good water circulation, wind and wave action within moderate limits. Excessive but protected from strong currents and high waves. It turbulence may lead to wastage of fish energy for stabilizing should be away from still or stagnant water where poor themselves, loss of feed and growth of weed also may not water quality may stress or kill fish and improper growth be proper. The other major considerations are that the water of the weed. It must be placed at least above 1 m above should be pollution-free, availability of seed in the vicinity, the bottom sediments. easy accessibility to the site and a ready market for fish and the weed. Flowing waters with a slow current of 1.0 to Water quality considerations 9.0 m per minute are considered ideal for cage siting. It is A good water area without any pollution is desired for desirable to install cages a little away from the shore to the culture of fish or shellfish and sea weed. Biofouling prevent poaching and crab menace but within the limit of caused by organisms that attach themselves to the cage reach by the persons who monitor daily the activities. and restrict water exchange. Area away from marine Species selection Selection of species for cage culture should be based on factors like the local demands and availability of quality seed, fast growth rate, adaptability to the stresses in enclosures biofouling organisms include algae, oysters, clams, and barnacles is suited or else cleaning at regular intervals are required to facilitate a good culture activity. Security considerations due to crowded conditions, ready acceptance of trash fish Cages should be placed where they can be easily feeds and good market demand. Seaweed is opted at places monitored if poaching is a serious consideration. where it can be disposed off as fast as possible. Methods applied Cage Materials, mooring and anchoring Experimental circular grow-out cage (15 m diameter and 6 The cage should be durable and strong, but light weight m deep) with floating frames was used for the purpose. and allow complete exchange of water volume every 30 Fingerlings of 80-95 mm average length which were reared to 60 seconds by using a minimum of 13-mm square mesh and acclimatized in 5 ton capacity FRP tanks at the size. There should be a free passage of fish wastes and mariculture hatchery of the regional centre were transferred should be inexpensive and readily available. It should have to the grow-out cage and reared at a suitable density. In a proper net to hold the crop as well as to protect from order to test the use of available space in the outer ring of the predators. The outer ring should have been supported the floating cage, thalli of the seaweed K. alvarezii were with cat walk for daily observation of the fish, weed and grown in nets tied with plastic rope to the HDPE outer ring 58 Central Marine Fisheries Research Institute From 14 - 23 December 2009 of the cage. Simultaneously, epoxy coated iron boxes (2 x 2 z Easier stock management and monitoring compared x 0.5 ft) with plastic net covering were used to grow the with pond culture and it shows the possibilities of spat of P. fucata were attached to the outer ring of the combining several types of culture within one water cage. The spats which were bred and grown in the body. mariculture hatchery of the centre were used to stock in z the boxes with the average initial DVM 45 mm, AVM 38 Easy for daily observation of the stock allows for better management. mm and cup width 13 mm and an average weight of 6.22 gm. Regarding management, fish was fed only with trash fish available at the Visakhapatnam fishing harbour at Disadvantages: z Stock is vulnerable to external environmental hazards different rates as per the biomass and no other management like cyclones and currents and the water quality was undertaken for the oysters and the seaweed. Sea weed problems like algal blooms and biofouling organisms. brought from Mandapam area of Ramanathapuram district Rapid fouling of cage walls requires frequent cleaning of Tamilnadu and it was grown in the mariculture hatchery of net. of Regional Centre of Central Marine Fisheries Research z Back up food store hatchery and processing are Institute, Visakhapatnam, Andhra Pradesh. It was cut it in necessary to overcome feeding in the fishing ban to fragments of 30 g each and allowed to grow further, in timings. the 1 ton FRP tanks with 30 ppt salinity and about 30% z Feed losses possible through cage walls due to water water exchange everyday. Further, it was grown in offshore currents and sometimes the small fish enter cages area of Lawson’s Bay at Visakhapatnam stocked in plastic and compete for food. net pouch of 0.5x05 ft. and the growth was recorded and compared with onshore culture conditions. After sufficient amount has been harvested it was re stocked in plastic net pouch of 2.0x2.0 ft. the outer floating frame of the open sea floating cage in square plastic rope nets of (2x2 ft) size in which 150 gms. of sea weed were stocked. Growth of oysters, seaweed and fish yield reached remarkable production rates with the increment in case of fish about 212.5 %, in case of oysters with 28.8 % in DVM, 23.68 % in AVM, 61.53 % in cup width and 296.62 % in weight and in case of seaweed the increment was 456.66 %. Advantages and disadvantage Advantages: z z z Security management is must to avoid poaching as the high density of crop is in confinement. Conclusion With the results presented, it can be concluded that in open sea floating cages, the cultivation of fish, sea weed and oysters either pearl producing or edible, provides a reasonable solution to cultivate species that are economically valuable and increase profitability without much investment. In the present study, the conditions of oysters and the seaweed were very healthy and no negative interferences could be observed in co-culturing fish, oyster and seaweed in the same cage indicating the treatments and harvests remaining independent. Further Use of existing coastal water bodies with possibility improvement with regard to designing of the system can of making maximum use with greatest economy with be done when battery of open sea floating fish cages are lower capital cost investment as compared to land- tagged to each other with sea weeds and oysters attached based farms. to the outer floating frames. It provides scope for further With its technical simplicity open sea floating cage research to incorporate with species that could grow well farms can be established or expanded which further and also act as an efficient biofilter for this integrated helps to reduce the pressures on land resources. system. 59 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Nutritional requirements of Asian seabass, Lates calcarifer Ambasankar, K., Ahamad Ali, S. and Syamadayal, J. Central Institute of Brackishwater Aquaculture No. 75, Santhome High Road, R.A. Puram, Chennai-600 028, Tamil Nadu ambasankar@ciba.res.in Introduction Asian seabass (Lates calcarifer ) has emerged as an important candidate finfish species for aquaculture in many parts of the world. Availability of seed and appropriate feed are the two important prerequisites for development and propagation of aquaculture of any fish species. After considerable efforts and extensive research, the Central Institute of Brackishwater Aquaculture (CIBA) has succeeded in developing captive brood stock and seed production technology for Asian seabass. Research efforts on nutritional requirements and development of suitable formulated feeds have been in progress simultaneously at CIBA. The nutritional requirements of fish vary with different growth stages and depend upon the feeding habits that change according to the morphology of digesting system. Considerable effort has been made in nutrient requirement in the diet. Recently information on micro-nutrient needs such as vitamins has started coming in. The nutrition research undertaken falls clearly into two streams viz., requirements during hatchery and nursery phase and requirement in grow out period. Requirements during hatchery and nursery phase The nutritional requirements of larvae that have a body mass less than few milligrams are not very much understood. Based on the composition of the yolk, live prey and larvae themselves it is assumed that the nutritional requirements of larvae were higher than those of the juveniles. The nutritional requirement is not similar for larvae and juveniles. Indeed, a dietary formulation sustaining good growth in juveniles induces poor results in larval growth and survival. Australia, Thailand, Philippines and more recently Israel, Most of the works conducted on nutritional requirements in defining the nutritional requirements of this species in in fish have focused on lipid requirements. Until a few order to improve production. Understanding the years ago as there was no compound diets available for nutritional requirements of the candidate species is the larvae, studies on nutritional requirements are limited in first and essential pre requisite for development of cost general. However, studies on lipid requirements were effective, efficient and eco friendly feeds. easier to conduct because total lipid content or fatty acid profile can be modified in live prey, while it is quite Nutritional requirements impossible to change the amino acid profile of an Investigations on Asian seabass (also known as Bhetki in organism. Nevertheless, growth is essentially protein Bengal, Koduva in Tamil, Kalanchi/ Narimeen in deposition, and adequate proteins must be supplied to Malayalam) have been mainly concentrated on energy sustain optimal growth. 60 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Lipid requirements Lipid sources and total lipid which are found in large amount in fish cell membranes. Experiments conducted using live prey (Watanabe and Kiron, 1994) or a compound diet (Zambonino Infante and Eggs of marine fish exhibit high lipid content around 20% Cahu, 1999) have shown that the optimal level of and reported that fertilized eggs of seabass contain about EPA+DHA in diet for marine fish larvae is around 3% of 27% lipid on DM basis (Syamadayal et al., 2003). Lipids dry matter. included in microparticulate diets come partly from fish meal or other meals incorporated as protein source and are generally derived from marine sources. Cod liver oil, Protein requirements Protein sources roe oil, sardine oil or menhaden oil are added as triglycerides in larval diets. In seabass larvae, growth and Person Le Ruyet et al. (1989) weaned 23-day-old seabass, survival were directly related to the lipid content of the Dicentrarchus labrax, with a compound diet including diet. Best results were obtained with the diet containing squid, shrimp and hen eggs. A mixture of fish meal, shrimp 30% lipid, as a mixture of cod liver oil and soy bean lecithin meal, squid meal, lactic yeast was used in a diet given to (Zambonino Infante and Cahu, 1999). 25-day-old seabass larvae (Zambonino Infante and Cahu, 1994). Protein sources were selected following their Phospholipid amino acid profile and incorporated in microdiet as the Beneficial effects of phospholipid (PL) incorporation in only protein source. Fish meal has been used as the main larval diet was reported as early as in 1981 (Kanazawa et protein source in diet formulated for seabass (Zambonino al.1981) and in 1993, he has reported that fish larvae were Infante et al., 1997) up to a level of 65% in the diet used incapable of synthesizing PL at a sufficient rate to meet for feeding 20 day post hatch (dph) larvae. The first the requirement during a period of high cell multiplication; attempt to determine optimal dietary protein level for hence PL is required in larval diets. Studies have been seabass at very young stages was conducted by feeding conducted at CIBA to determine optimal level of larvae from Day 15 to Day 35 with isoenergetic compound phospholipids in seabass larvae using soybean lecithin as diets incorporating a gradient in protein level (fish meal phospholipid source. Good growth and survival have been plus casein hydrolysate @ 30-60%). The best growth was obtained by feeding seabass larvae with a diet containing obtained with 50% protein. fish oil and lecithin at 5 and 10% respectively. Sargent et al. (1999) are of the opinion that the ideal diet for marine Amino acid requirements fish larvae would include 10% marine fish phospholipid, No information is available on the amino acids since egg or yolk sac larvae exhibit 10% phospholipid requirement for marine fish larvae and their optimal level concentration. in a diet. However, the profiles of essential amino acids Essential fatty acid The n-3 highly unsaturated fatty acids (HUFA) have been identified as essential dietary components for marine fish of fish body tissue are generally considered as a good indicator of their amino acid requirements. Molecular form of the protein fraction since a long time as marine fish cannot synthesize them. The role of free amino acids and short peptides in diet on Special attention was paid to eicosapentaenoic (EPA, larval development has been investigated by several C20:5n-3) and docosahexaenoic acid (DHA= C22:6n-3), authors. As early as 1989, Fyhn (1989) suggested that 61 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi free amino acids constitute a substrate for energy growth improvement when an amino acid mixture failed production in marine fish larvae during early larval stages to induce the same effect. Hydrolysates are beneficial to and the larvae during young stages need an exogenous larvae, while they do not affect, or in some cases, depress supply of free amino acids. Watanabe and Kiron (1994) juvenile growth. These results suggest that fish larvae have considered that it is not clear if fish larvae have a sufficient specific nutritional requirements which can be understood ability to digest food protein or whether free amino acid by the analysis of larval digestion. must be provided by diet. In the same way, the incorporation of 10% essential amino acid mixture in fish Nutritional factors affecting larval morphogenesis meal based diet failed to improve growth and survival in Protein hydrolysate enhances larval morphogenesis. The seabass larvae compared with larvae fed diet with the molecular form of the dietary protein supply, native same nitrogenous level brought as whole protein (Cahu proteins or hydrolyzed into oligopeptides (around 20amino and Zambonino Infante, 1995). Nevertheless, the dietary acids), has probably an indirect effect on morphogenesis. incorporation of free amino acids induced an increase in Dietary lipids play an essential role in larval growth and trypsin secretion in early larvae stages suggesting that survival. Growth and normal morphogenesis increased as pancreatic digestion would be improved. Beside their the dietary inclusion of phospholipids and vitamins, nutritional function, free amino acids play a very important particularly vitamin A. role in first feeding by acting as chemo-attractant. Protein hydrolysate has been since a long time considered as an Requirements during grow - out phase advantageous protein form for fish larvae and the product Protein and amino acids constitute the key group of was incorporated in most of the larval diets at least for essential nutrients required by Seabass for synthesis of improving microparticle physical properties. Recent protein and subsequently growth. Several studies have experiments have shown evidence of the high nutritional been undertaken to define protein requirements, although value of protein hydrolysate and its role in larval nutrition. limited studies have been undertaken to examine specific Zambonino Infante et al. (1997) showed that a 20% requirements for key amino acids. replacement of fish meal by di and tripeptides (obtained from fish meal hydrolysate) in diet resulted in Protein improvement of the main biological parameters in seabass Most of the studies undertaken to examine the larval rearing: growth, survival and skeletal formation. requirements for protein in barramundi diets suggest a Incorporating di- and tri-peptides to the diet led to a relatively high protein requirement, consistent with the Table 1. Summary of protein requirement estimates for barramundi Crude Protein levels examined (% to %) 35 - 55 45 - 55 45 - 55 n/d 35 - 50 29 - 55 38 - 52 44 - 65 Optimal Level (%) (MJ/kg) 45 - 55 50 45 40-45 50 46 - 55 52 60 Gross Energy level at Optima Initial Fish Size (g) Temp (C) 13.4 – 16.4 n/d n/d n/d 50 18.4 – 18.7 17.8 – 21.0 20.9 – 22.8 n/d 7.5 n/d n/d 1.3 76 230 80 n/d n/d n/d n/d 29 28 28 28 Authors Cuzon, 1988 Sakaras et al. 1988 Sakaras et al. 1989 Wong and Chou, 1989 Catacutan and Coloso, 1995 Williams and Barlow, 1999 Williams et al. 2003 Williams et al. 2003 62 Central Marine Fisheries Research Institute From 14 - 23 December 2009 carnivorous/ piscivorous nature of the fish. Seabass being crystalline amino acids into a lower protein diet. Both highly carnivorous showed a dietary requirement of 45 – studies showed that the utilisation of the crystalline 55% protein. Subsequently Catacutan and Coloso (1995) amino acids was as effective as that of protein-bound suggested 42.5% in the diet of the fish. Experiments amino acids, but only at the low inclusion levels in the conducted in CIBA with different level protein feeds on high-protein diet. Estimations of essential amino acid the young-ones of seabass showed a protein requirement requirements have also been made based on the of 43 % for this fish. The summary of protein requirement composition of the body tissues relative ratios of key as reported in the literature is given in Table-1.The protein amino acids to lysine, usually regarded as the first limiting quality in the feed influences the requirement. amino acid in most formulated diets. The diet energy density and the size of fish used, appear Lipid to be the key factors influencing the specific amount of protein required for seabass. Amino acids Most of the finfish including seabass show the requirement of the same ten amino acids (arginine, histidine, isoleucine, leucine, lysine, methionin, phenylalanine, threonine tryptophan, tyrosine or valine) as essential. However, determination of quantitative essential amino acid requirement would help in assessing the protein requirement more accurately. There have been several estimates of some specific amino acid requirements for barramundi. Coloso et al. (1993) estimated the requirement for tryptophan to be about 0.5% of dietary protein. The requirements for methionine, lysine and arginine have also been determined to be about 2.2%, 4.9% and 3.8% of dietary protein respectively (Millamena et al. 1994). It has been reported that excessive dietary tyrosine can cause kidney malfunction in barramundi (Boonyaratpalin, 1997). Lipids comprise an important dietary energy source for seabass and are also a source of essential fatty acids. Much work has been devoted to exploring the inclusion of lipids in barramundi diets to increase their energy density. At protein levels of 45% to 50% Sakaras et al. (1988; 1989) observed best growth from barramundi fed diets with 15% to 18% lipid content. Studies also showed a similar growth from barramundi fed diets with either 9% or 13% lipids, but noted that feed conversion ratio was significantly lower with the higher lipid levels. Studies by Catacutan and Coloso (1995) examined inclusion levels of 5%, 10% and 15% lipids with three protein levels (35%, 42.5% and 50%). Growth rate was highest at the 15% lipid level, provided protein was also at the highest levels (50%). Similar growth was also observed of fish fed diets with 10% lipids and 42.5% protein. Somatic deposition of fat was observed to increase with dietary fat levels. In a study of some extruded commercial diets, Glencross et al. (2003) found that two diets of similar protein levels, but differing substantially in lipid levels (16% vs. 22%) sustained equivalent growth A series of experiments by Australian researchers of 555 g fish, but that the higher lipid levels resulted in a examined the capacity of barramundi to utilise crystalline significantly lower feed conversion ratio. These authors and protein-bound amino acids. One study, based on the suggested that this was primarily a response by the fish addition of crystalline lysine to a wheat gluten based, to the energy density of the diets. high-protein diet, compared its utilisation to complementary diets modified to have an equivalent level Essential fatty acids of lysine enrichment, but with protein-bound amino acids. Long-chain polyunsaturated fatty acids have been shown A second study examined the similar addition of to provide some essential fatty acid (EFA) value to 63 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi barramundi (Boonyaratpalin, 1997). Boonyaratpalin (1997), carbohydrates. It can derive dietary energy from some suggested that n-3 EFA levels (primarily as a mix of 20:5n- carbohydrate sources. Research findings infer that 3 and 22:6n-3) of 1.0% to 1.7% of the diet were adequate carbohydrate as gelatinised bread flour had some capacity to support growth. Catacutan and Coloso (1995) to provide dietary energy to barramundi. Fish fed diets that examined the total lipid levels and observed signs of EFA were iso-lipidic and iso-proteic with 20% carbohydrate deficiency (fin erosion) at 5% dietary lipid levels. performed better than those with only 15% carbohydrates. Growth was significantly affected by the replacement of Vitamins fish oil with either canola or linseed oils, but not with The quantitative requirements of vitamins and their soybean oil. This observation may be due to the altered deficiency signs in the fish are presented in Table. 2 Table 2. Summary of vitamin requirements (mg/kg of diet) for barramundi Vitamin Requirement (mg/kg diet) Deficiency Signs Thiamine R Poor growth, High mortality, Stress susceptible Riboflavin R Erratic swimming, Cataracts Pyridoxine 5 – 10 Erratic swimming, High mortality, Convulsions Pantothenic acid 15 – 90 High mortality Nicotinic acid n/a Fin hemorrhaging and erosion, Clubbed gills, High mortality Biotin n/a Inositol R Choline n/a Folic acid n/a Ascorbic acid (Vitamin C) 25 – 30a (700b) Vitamin A n/a Vitamin D n/a Vitamin E R Vitamin K n/a Poor growth, Abnormal bone formation Gill hemorrhages, Exophthalmia, Scoliosis, Lordosis, Broken back syndrome, Fatty liver, Muscle degeneration, Poor gill development, Bone deformations Muscular atrophy, Increased disease susceptibility n-3 to n-6 ratios. Soybean oil is about 60% linoleic acid (18:2n-6) and therefore would have substantially altered the ratios of the diets more so than either canola or linseed oils, both of which have substantially higher levels of n-3 fatty acids than soybean oil. An optimal n-3 to n-6 fatty acid ratio of 1.5-1.8:1 reported for seabass with an increase in demand at higher water temperatures. A “shock-like” or “fainting” response was observed in some barramundi Summary of nutrient requirements for seabass: Nutrient Protein Lipid Fatty acids Requirement in diet 45 – 55% 6 - 18% 1.72% (n-3 HUFA essential) Carbohydrate Protein : Energy ratio Vitamin C 10 – 20% 128mg protein/kcal 700 mg/kg from treatments where there were low levels of n-3 EFA. References Carbohydrates Asian Seabass have no specific requirement for dietary Boonyaratpalin, M. 1997. Nutrient requirements of marine food fish cultured in Southeast Asia. Aquaculture 151, 283-313. 64 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Cahu, C. L., Zambonino Infante, J. L. & Barbosa, V. (2003). Effect of dietary phospholipid level and phospholipid:neutral lipid value on the development of seabass (Dicentrarchus labrax) larvae fed a compound diet. Br. J. Nutr. 90, 21-8. Sakaras, W., Boonyaratpalin, M., Unpraser, N., Kumpang, P. 1989. Optimum dietary protein energy ratio in seabass feed II. Technical Paper No. 8. Rayong Brackishwater Fisheries Station, Thailand, 22 pp. Cahu, C.L. and Zambonino Infante, J.L. 1995. Maturation of the pancreatic and intestinal digestive functions in seabass (Dicentrarchus labrax): effect of weaning with different protein sources. Fish Physiol. Biochem., 14: 431-437. Sargent, J., Bell, J.G., Bell, M.V., Henderson, R. J. and Tocher, D.R. 1993. The metabolism of phospholipids and polyunsaturated fatty acids in fish. In: Lalhou, B. and Vitiello, P. (Eds), Aquaculture: Fundamental and Applied Research. Coastal and Estuarine Studies, American Geophysical Union, Washington D.C., 43, pp 103-124. Catacuttan,M.R. and Coloso, R.M. 1995. Effect of dietary protein to energy ratios on growth, survival, and body composition of juvenile Asian sea bass, Lates calcarifer. Aquaculture 131, pp. 125–133 Coloso, R.M., Murillo, D.P., Borlongan, I.G. Catacutan, M.K., 1993. Requirement of juvenile seabass Lates calcarifer Bloch, for tryptophan. In: Program and Abstracts of the VI International Symposium on Fish Nutrition and Feeding, 4-7 October 1993, Hobart, Australia. Fyhn, H.J., 1989. First feeding of marine fish larvae: are free amino acids the source of energy? Aquaculture, 80: 111-120. Sargent, J., Mc Evoy, L., Estevez, A., Bell, G., Bell, M., Henderson, J. and Tocher, D. 1999. Lipid nutrition of marine fish during early development: current status and future directions. Aquaculture, 179: 217-229. SyamDayal, J. Ali, S.A., Thirunavukkarasu, A.R., Kailasam, M. and Subburaj, R.2003. Nutrient and amino acid profiles of egg and larvae of Asian seabass,Lates calcarifer (Bloch). Fish Physiol. Biochem. 29: 141–147 Glencross, B.D., Rutherford, N., Hawkins, W.E. 2003. Determining waste excretion parameters from barramundi aquaculture. Fisheries Contract Report Series No. 4. Department of Fisheries, Perth, Western Australia. pp 48. Wanakowat, J., Boonyaratpalin, M., Pimolindja, T, Assavaaree, M. 1989. Vitamin B6 requirement of juvenile seabass Lates calcarifer . In: The Current Status of Fish Nutrition in Aquaculture (M. Takeda and T. Watanabe Eds.), Tokyo University of Fisheries, Tokyo, Japan, pp. 141-147. Kanazawa, A., 1993. Essential phospholipid of fish and crustaceans. In: Kaushik, S.J. and Luquet, P. (Eds), Fish Nutrition in Practice, Edition INRA, Paris, Les Colloques n°61: 519-530. Watanabe, T. and Kiron, V. 1994. Prospects in larval fish dietetics. Aquaculture 124: 223-251. Kanazawa, A., Teshima, S. Inamori, S., Iwashita, T. and Nagao, A. 1981. Effect of phospholipids on growth, survival rate and incidence of malformation in larval ayu. Mem. Fac. Fish., Kagoshima Univ., 30: 301-309. Williams, K.C., Barlow, C.G. 1999. Dietary requirement and optimal feeding practices for barramundi (Lates calcarifer). Project 92/ 63, Final Report to Fisheries R&D Corporation, Canberra, Australia. pp 95. Millamena. O.M. 1994. Review of SEAFDEC/AQD fish nutrition and feed development research. In: Feeds for Small-Scale Aquaculture, Proceedings of the National Seminar-Workshop on Fish Nutrition and Feeds (C.B. Santiago, R.M. Coloso, O.M. Millamena, I.G., Borlongan). SEAFDEC Aquaculture Department, Iloilo, Philippines., pp. 52-63. Williams, K.C., Barlow, C.G., Rodgers, L., Hockings, I., Agcopra, C., Ruscoe, I. 2003. Asian seabass Lates calcarifer perform well when fed pellet diets high in protein and lipid. Aquaculture 225, 191-206. Phromkunthong, W., Boonyaratpalin, M., Storch, V. 1997. Different concentrations of ascorbyl-2-monophosphate-magnesium as dietary sources of vitamin C for seabass, Lates calcarifer. Aquaculture 151, 225-243. Zambonino Infante, J.L. and Cahu, C.L. 1994. Influence of diet on pepsin and some pancreatic enzymes in sea bass (Dicentrarchus labrax) larvae. Comp. Biochem. Physiol., 109: 209-212. Ronnestad, I., Thorsen, A. and Finn, R.N. 1999. Fish larval nutrition: a review of recent advances in the roles of amino acids. Aquaculture, 177: 201-216. Zambonino Infante, J.L. and Cahu, C.L. 1999. High dietary lipid levels enhance digestive tract maturation and improve Dicentrarchus labrax larval development. J. Nutr., 129: 11951200. Sakaras, W., Boonyaratpalin, M., Unpraser, N., Kumpang, P. 1988. Optimum dietary protein energy ratio in seabass feed I. Technical Paper No. 7. Rayong Brackishwater Fisheries Station, Thailand, 20 pp. Zambonino Infante, J.L., Cahu, C.L. and Péres, A. 1997. Partial substitution of di- and tripeptides for native proteins in sea bass diet improves Dicentrarchus labrax larval development. J. Nutr. 127: 608-614. 65 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Feeds and feeding of seabass in hatchery, nursery and grow out system using formulated feeds Ambasankar, K., Ahamad Ali, S. and Syamadayal, J. Central Institute of Brackishwater Aquaculture No. 75, Santhome High Road, R.A. Puram, Chennai-600 028, Tamil Nadu ambasankar@ciba.res.in The requirement of nutrients varies throughout the life developing larvae do not have the full complement of cycle of an individual. At early stages, the requirement of digestive system developed. The larvae of seabass are no nutrients is comparatively high which declines with age. exception to this. Studies conducted at CIBA on the Also the requirements depend upon the feeding habits metabolic changes and nutrient turn-over in developing that change accordingly to the morphology of digestive seabass larvae revealed that the growing larvae require system. Considerable effort has been made in Australia, the essential amino acids leucine and lysine at higher Thailand, Philippines and more recently Israel, in defining levels in the larval diets (Syama Dayal et al., 2003). Being the nutritional requirements of seabass in order to improve carnivorous, seabass larvae are fed with zooplankton such production (Boonyaratpalin and Williams, 2001). Feeds as rotifers for the first two weeks post hatch (PH) and and feeding are the critical factors that determine the then switched over to brine shrimp (Artemia) nauplii. The economic viability of commercial aquaculture of the size of the rotifers plays an important role in the successful species concerned and this topic assumes much more rearing of the larvae. Super small size rotifers are preferred significance in a carnivore species like seabass. Based on for feeding seabass larvae. Since, Artemia is an expensive the nutritional requirements we know that this fish live-food, its replacement by prepared diets has assumed requires a high protein high energy diet. Further, being a significance in the hatchery and nursery rearing of fish predatory carnivore in nature, weaning them to formulated larvae. In this context, formulated micro particulate and feed is the critical factor which influences the success of microencapsulated diets have been successfully used for grow out culture of seabass. Understanding the nutritional feeding the growing fish larvae. requirements of the candidate species is the first and essential pre- requisite for the development of cost Compounded micro diets for seabass larvae effective, efficient and eco friendly feeds. Physical aspects Feeding of larvae in hatchery and nursery Size Larvae of finfish and shellfish are generally fed with live Diet must be prepared as microparticles, whose size must food organisms (phytoplankton or zooplankton or both) be adapted to the size of the larval mouth. As an example, in the initial phase. Investigations revealed that the size of the microparticulated diets used for seabass larval 66 Central Marine Fisheries Research Institute From 14 - 23 December 2009 experiments was 50 to 125 µm at first feeding, then 125- matrix such as agar, carrageenan or calcium alginate or by 200 µm from Day 14 to Day 25, then 200-400 µm to a protein such as casein or zein. Microencapsulated diets Day 40 (Cahu and Zambonino Infante, 1994). The size of are prepared with a cross-linking agent. Microencapsulation commercial microparticles used in hatchery for seabass produces regular shape and water stable microparticles, but or sea bream weaning, used from Day 40, is generally the microcapsules can be difficult to digest. The ability of 400 to 600 µm. Accurate size of the microparticles is larvae to break microcapsules depends on the thickness of essential and must be well calibrated to minimize waste. the capsule coating. Particularly, small microparticles (less than 50 µm Buyoancy of the diet diameter) cannot be easily detected by larvae, whereas large ones are difficult to ingest and may even promote a Dietary microparticles must be distributed in large excess. blockage of the digestive valve (Walford et al., 1991). The Indeed, early stage larvae have a limited movement and composition of microparticles must be homogenous; microparticles must be caught during their fall in the water hence, ingredients must be incorporated as very fine meal. column. Good results can be obtained with low density The size of the meal particles must be much smaller than microcapsules (400-600 g/L), sinking at about 25 cm/h the size of the final dietary microparticle. Diet, such as average. fish meal, must be ground and sieved before being Visual and chemical stimuli of the diet included in microparticles. Concerted efforts made by CIBA scientist lead to the development of micro diets for Light intensity, color of microparticles and tank are essential seabass larvae and the different micro diets used for larval for ingestion. Some pigments, such as asthaxanthin, have rearing are given below. been incorporated in microparticles, more for improving the Micro diets developed at CIBA for seabass larvae MD-200 MD-300 MD-400 Manufacturing techniques visibility of the particle by larvae than for their nutritional Nutrient leaching is one of the problems in developing value. Free amino acids, such alanine, glycine and arginine suitable diets for fish larvae. Particles must be water-stable, and the compound betaine, have been identified as efficient palatable and digestible. Diets used for late weaning (after chemical stimulator for microdiet in gilthead sea bream Day 40) in the hatchery can be crumbled, prepared by larvae (Kolkovski et al., 1997). grinding and sieving pellets, but diets of smaller size must be prepared in microbound, microcoated, or Thus, larval feed development largely depends on: microencapsulated form. In microbound diets, the z Selection of nutrient specific to the species powdered ingredients are microbound with a water stable z Nutritional balance of formulation 67 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi z Retention of nutritional components Micro diets distribution z Homogeneity of particles The major bottleneck associated with micro diets feeding z Particle size and distribution are over feeding of larvae and pollution of the z Density of particles z Water solubility initially and then fall to the bottom. The larvae are not z Storage stability interested in diet that are floating or lying at the bottom z Packing requirements environment. The food particles must be made available in large number around the larvae. Small particles float of the tank but fed on those particles that pass by their vicinity. Feeding frequencies and feeding period has to be Apart from providing a balanced diet, the other problem extended as the larvae are very sensitive to starvation. related to larval rearing is the weaning of larvae. Some of However, they can not ingest their daily ration in two to the larvae tend to grow faster naturally than the other in three meals as the resting time in the digestive tract of the stock, which have to be segregated time to time for larvae are very short compared to juveniles. These features higher survival ability and production. These fast growing of larvae necessitate continuous and excess feeding. Thus, ones are not necessarily due to nutritionally imbalanced it is essential to use feeders in larval rearing of seabass feed but could be due to number of other factors that the using micro diets. hatchery operator usually faces. Feeds and feeding of seabass in grow-out culture Practical feeding of micro diets in sea bass larval rearing Weaning The age at which weaning is carried out varies considerably depending on the larval size and rearing method employed. The use of micro diets in larvae is essentially preceded by weaning them to formulated diets. The weaning of larvae can be carried out in following ways: 1. By having a intermediate feeding phase using frozen or freeze dried zooplankton 2. Using simultaneous distribution of live prey and dried feed. It can be started at an early stage. 3. Co-feeding but shortening the live prey co feeding to one or two days. This results in better size homogeneity In some of the East Asian countries and also in India, seabass is cultured in grow-out ponds using low value fish (trash fish) and tilapias in fresh condition. Since, procurement and storage of these feed-fish is not only laborious but also quite expensive. Hence, formulated feeds are essential for the propagation of large-scale farming of seabass. Asian seabass is cultured in Australia and Thailand using formulated feeds (Boonyaratpalin, 1991). As in the case of other carnivorous species, feed formulations for seabass utilize marine fish resources (for meeting protein requirement) and fish oils along with plant protein sources. The animal ingredients are kept above 60% of the formulation to get protein levels in the range of 45-52%. Experiments conducted at Muttukadu field laboratory of CIBA had shown that feeds with substantial fishmeal component (30-40%) only have good acceptability for 4. Starving the larvae and then introducing the micro seabass. Higher the proportions of fishmeal better the diets. This method can only be practiced in larvae acceptability. The texture and size of the feed affects which are in good health acceptability of the feed. If the flavour and texture of the 68 Central Marine Fisheries Research Institute From 14 - 23 December 2009 feed are not to the liking of the fish, it spits out the feed fed into an extruder by proper arrangement of water/ soon after ingesting. The use of animal protein sources steam injection facility. The extruder operates at high such as fishmeal is inevitable in order to keep higher pressure (14 98 kg/cm2) and steam (Pressure 5 7 kg/cm2) protein levels in the feed. However, plant ingredients such injection. Depending upon the characteristics of the feed soybean meal and other oil seed residues may be utilized mixture and moisture content, the pressure develops in the feed formulations. Marine fish oils should be before the material passes through the die. Because of included in the feed formulations as a source of this the temperature rises and the material is forced polyunsaturated fatty acids (PUFA). Studies conducted through the die and the pressure suddenly drops. The at CIBA revealed that the amino acid, glutamic acid, is a temperature of the material rises to 110 useful feed attractant for seabass. short spell of time and cooks the food, gelatinizing the Seabass feeds on moving prey; hence the physical design of the feed plays a very important role. The fish readily accepts soft semi-moist feeds with appropriate size to swallow vis-à-vis the size of the fish. The lower lip of the fish is curved slightly upward, which pose disadvantage while biting the feed. Floating and slow sinking pellet feeds are more suited for feeding seabass. Such feeds are generally processed in extruders. 130oC for a starch present in the feed mixture. This imparts good binding and water stability to the resultant pellets. However, the pellets expand as they come out of the die due to sudden drop of pressure and air gaps develop inside the pellet, which makes them float or sink very slowly. This is an excellent process for producing floating pellets for finfish culture. By adjusting the pressure in the barrel and moisture in the feed, it is possible to prepare sinking pellets by extruder. The new generation extruders are made with twin screw barrel arrangement, which are more versatile for feed manufacture. The size of the pellet diameter ranges from 0.5 mm to 8.0 mm. The characteristics of extruder pellets are Sinking feeds for seabass z Reduction in pellet disintegration and loss in water. z Increases starch digestibility due to good cooking z Can be worked with higher moisture and oil (fish oil) levels in the feed. z Extruder pellets float or sink slowly. z Making charges for extruder pellets are higher due to high cost of extruders At CIBA, formulated feeds developed as floating and sinking pellets were successfully tested in grow-out ponds Floating feeds for seabass and the fish growth was found to be 500 g in six months. Extruder technology The fish should be fed at the rate of 10% of their body The basic components in an extruder are a barrel fitted weight to start with. After four to six weeks the feeding with a die plate and a screw shaft conveyer, which is rate may be reduced to 8%. As the fish grow in size the connected to a high-speed motor. The feed mixture is feeding rate should be gradually reduced to 5%, 3% and 69 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi finally 2%. The total biomass in the pond should be periodically estimated by suitable means (by caste netting) for adjusting the feed. The entire quantity of feed in a day should not be given at one time but divided and fed 3-4 times a day. References Boonyaratpalin, M. 1997. Nutrient requirements of marine food fish cultured in Southeast Asia. Aquaculture 151, 283-313. Boonyaratpalin, M., Williams, K.C. 2001. Asian sea bass, Lates calcarifer. In: Nutrient Requirements and Feeding of Finfish for Aquaculture (C.D. Webster and C.E. Lim Eds.). CABI Publishing, Wallingford, UK. pp 40-50. Cahu, C.L. and Zambonino Infante, J.L. 1994. Early weaning of sea bass (Dicentrarchus labrax) larvae with a compound diet: effect on digestive enzymes. Comp. Biochem. Physiol., 109A: 213-222. Kolkovski, S., Koven, W. and Tandler, A. 1997. The mode of action of Artemia in enhancing utilization of microdiet by gilthead seabream Sparus aurata larvae. Aquaculture, 155: 193-205. SyamDayal, J. Ali, S.A., Thirunavukkarasu, A.R., Kailasam, M. and Subburaj. R.2003. Nutrient and amino acid profiles of egg and larvae of Asian seabass,Lates calcarifer (Bloch). Fish Physiol. Biochem. 29: 141–147 Walford, J., Lim, T.M. and Lam, T.J. 1991. Replacing live foods with microencapsulated diets in the rearing of sea bass (Lates calcarifer) larvae: do they ingest and digest proteinmembrane microcapsules? Aquaculture, 92: 225-235. 70 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Success in hatchery development of seabass and its potential for commercial cage culture in India Thirunavukkarasu, A. R., Kailasam, M. and Sundaray, J. K. Central Institute of Brackishwater Aquaculture No. 75, Santhome High Road, R.A. Puram, Chennai-600 028, Tamil Nadu artarasu@hotmail.com Introduction Brackishwater fish farming is considered as one of the potential areas not only as a source for fish production but also ensures the food security, livelihood for coastal community, business opportunity for entrepreneurs and water bodies, which is suitable for fish farming under cages or pens can be also explored to increase the fish production in all maritime states of India. Culture potential also can earn foreign exchange. Coastal aquaculture has Among the brackishwater finfish species, the Asian grown tremendously in early 1990s with farming of single seabass, Lates calcarifer is considered as one of the most species, the tiger shrimp Penaeus monodon. However, important candidate species suitable for farming in ponds the shrimp farming faced severe set back due to outbreak and cages in fresh, brackish and marine water ecosystem. of viral diseases coupled with social and other Asian Seabass popularly known as Bhetki in India is an environmental issues. To overcome these issues, it is important brackishwater finfish of the family important to introduce some of the remedial measures in Centropomidae. The demand for seabass both in domestic order to revive the aquaculture industry to achieve the market and international market is increasing every year sustainable production and one such measure clearly because of its white tender meat. visible is the diversification of brackishwater aquaculture with fish species. It is evident that crop rotation can also Development of hatchery technology decrease the risk of disease outbreak in the pond system. Successful seed production in the hatchery depends upon In the recent years, reduction in large scale practices of the availability of healthy matured fishes. For selecting shrimp farming can be seen in most of the countries, potential breeders, viable broodstock under captive which is not only due to viral disease outbreak but also conditions has to be developed. Since seabass attains due to other reasons such as non availability quality and maturity after 2 years of age, one has to wait more than disease free shrimp seed, low in market price, increasing 2 years. To save time, adult fishes could be procured from production cost etc., Due to these factors, most of the the commercial catches, transported carefully to the established shrimp farms have been kept idle without any hatchery holding facilities and maintained. Healthy farming practice. Besides, a rich resource of inland coastal broodstock fishes after observing as protocols can be 71 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi transferred to broodstock holding facilities like RCC tanks administration of the hormones responsible for maturation (preferably large tanks of 50 – 100 tonne capacity) or and spawning. Seabass spends most of its growing phase cages or ponds for further maintenance and development in confined waters in the coastal and inland areas and providing required feed, quality water and healthy diet migrates to sea for maturation and spawning. for maturation and spawning. Induced spawning and selection of spawners Water Quality Management Spawning is a “process of release of sexual gametes”. Broodstock fishes maintained in captive condition should Since sexes are separate in the fish, both male and female be provided with environmental quality prevailing in the matured fishes have to be selected for spawning. The sea for maturation and spawning. The desirable range of fertilization is external. some of the water quality parameters in a broodstock tank are Matured female fishes will have ova with diameter more than 450 µ. Males will ooze milt if the abdomen is gently pressed. Temperature - 28 – 32 C The gonadal condition is assessed by ovarian biopsy. Brood Salinity - 28 – 33 ppt fishes selected for induction of spawning should be active, pH - 7.0 to 8.2 0 Dissolved oxygen - more than 5 ppm free from disease, wounds or injuries. Female fishes will be around 4 – 7 kg and males will be 2.0 – 3.0 kg. Since seabass spawning is found to have lunar periodicity, days of new moon Ammonia - less than 0.1 ppm or full moon or one or two days prior or after these days are Nitrite-N - less than 0.01 ppm preferred for inducing the spawning. Feeding and health management Induced spawning by hormone injection Brood fishes can be fed with trash fishes such as Tilapia The commonly used hormones in the finfish hatcheries or Sardines at the rate 5% body weight daily. The unfed for induced spawning are: feed can be removed carefully to avoid the contamination. Fishes have to be examined monthly basis to check the LHRH-a - Luteinizing Hormone Releasing Hormone analogue (Available with SIGMA parasitic infection if any. External parasites such as CHEMICALS – USA – ARGENT CHEMICALS) Caligus spp. and monogenic trematode, Diplectenum latesi, can be effectively treated either with 100 ppm HCG - Human Chorionic Gonadotropins. (Available in Pharmacy – medical shops) formalin for one hr or 1 ppm dichlorvos for one hour. Maturation Seabass is a protandrous hermaphrodite fish. They are males during early stage of its life cycle and become females in later period. Reproductive system is very much complicated in hermaphrodite fishes since they go through different phases of hormone secretion which is responsible Ovaprim - A Glaxo Product But in the case of seabass LHRH-a hormone is found to be effective with assured result though other hormones can also be used singly or in combination. Hormone dose for gonadal development. Maturation process can be After selecting the gravid fishes the requirement of induced/ accelerated either by simulating the hormone to be injected is assessed. The dosage level has environmental conditions prevailing in sea or through the been standardized as LHRHa at the rate 60 – 70 µg/kg 72 Central Marine Fisheries Research Institute From 14 - 23 December 2009 body weight for females and 30 – 35 µg/kg body weight is done during new moon/full moon Seabass has high for males. The hormone in the vial (normally 1 mg) is fecundity. It is a protracted intermittent spawner dissolved in distilled water of known volume (5 ml). Care (releasing eggs batch by batch). In one spawning the fish should be taken that hormone is thoroughly dissolved. may release 1.0 – 3.0 million eggs. The process of The weight of the brood fishes is assessed and the required spawning will follow during subsequent day also. If the hormone is taken from the vials using a syringe. The fish condition is good, both female and male respond is held firmly. After removing one or two scale just below simultaneously resulting spontaneous natural spawning the dorsal fin – above the pectoral region the syringe and fertilization is effected. needle is inserted into the muscular region and the hormone is administered intramuscularly gently. Since the spawning normally occurs in the late evening hours, when the temperature is cool, hormone is injected normally in the early hours of the day between 0700 – 0800 hours. Spawning tanks Spawning tanks size depends upon the size of the fish selected. Normally 10 – 20 tonne capacity tanks with provision for water inlet, drainage, overflow provision and aeration is used. Sex ratio Female seabass are generally larger (more than 4 kg.) and the males are smaller (in the size of 2.0 – 3.0 kg). To Fertilization Fertilization is external. In natural spawning of seabass in good maturity condition, fertilization will be 70 – 90%. The size of the fertilized eggs will be around 0.75 – 0.80 mm. The fertilized eggs will be floating on the surface and will be transparent. The unfertilized eggs will be opaque and slowly sink to bottom. Due to water hardening sometime, even the unfertilized eggs, for short duration will be on the sub-surface but will sink subsequently. The fertilized eggs can be collected by any one of the following methods. Overflow method ensure proper fertilization normally two males are After spawning and fertilization, the water level in the introduced for one female in the spawning tank. spawning tanks can be increased and allowed to overflow through overflow outlet. The eggs will be pushed by the Spawning water flow. Below the overflow pipe a trough covered Fishes injected with LHRH-a hormone response for with bolting cloth of mesh size 150 – 200 µm is kept. spawning after 30 – 36 hours of injection. Prior to The water with the egg is allowed to pass through. The spawning gradual swelling of the abdomen will be seen eggs are collected in the next bolting cloth washed and indicating the ovulation process. Spawning normally transferred to the incubation tanks. occurs late in the evening hours 1900 – 2000 hours. At the time of spawning the fishes will be moving very fast Scooping/ seine net collection method and in the water surface a milky white substance will be Since fertilized eggs will be floating on the surface, a seen. Prior to spawning activity the males and the female will be moving together exhibiting courtship. bolting net cloth of 150 – 200 µm mesh size can be used for collecting the eggs from the surface. The cloth is Spawning activity in seabass coincides with lunar stretched as net and towed along the water surface. The periodicity. During full moon or new moon days, the collected eggs after washing are transferred to the activity is found to be in peak. Hence, induced spawning incubation tanks. 73 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi tanks. Larvae are stocked initially at the rate 40 – 50 Siphoning method The water in the spawning tank is siphoned into small tank covering with collection net cloth through which the water will be allowed to pass through. The eggs collected in the net cloth are transferred periodically to nos/litre. Depending upon the age and size, the larval density is reduced to 20 – 25 nos/l on 10th day and later and after 15 days, the density is maintained around 10 – 15 nos/l. incubation tanks. Feeding the Larvae & Live Feed production Incubation and hatching The following live feeds are very important for feeding The eggs collected from the spawning tank are washed to remove the debris that would have adhered to and the larvae Algae Green unicellular algae like Chlorella sp., transferred to the hatching tanks for incubation and Tetraselmis sp., Nannochlorpsis or Isochrysis sp. hatching. The hatching incubation tanks can be 200 – are needed for feeding the live feed zooplankton. 250 L capacity cylindro-conical tanks. Eggs are kept at density of 100 - 200 nos/litre. Continuous aeration is Rotifer rotundiformis is the most preferred diet for provided. Temperature of 27 – 280C is desirable. The eggs will hatch out in 17 – 18 hours after fertilization undergoing developmental stages are given in the following Table: Rotifer ( Brachionus plicatilis ) or B. the fish larvae in their early stages. Artemia Brine shrimp, Artemia in nauplii stage are required for feeding the larvae from 9th day. Artemia with its natural nutrient profile Embryonic development Stages Duration required for larval development of fish is used One Cell stage Two Cell stage Four Cell stage Eight Cell stage Thirty two Cell stage Sixty four Cell stage 128 Cell stage Blastula stage Gastrula stage Neurula stage Early embryo Heart functional and tail movement Hatching 30 minutes 40 minutes 45 minutes 60 minutes 2 hrs 2 hrs 30 minutes 3 hrs 5 hrs 30 minutes 6 hrs 30 minutes 8 hrs 11 hrs 15 hrs 17 – 18 hrs in all the hatcheries. . Whatever good the culture system may be in many cases, Rotifer or Artemia nauplii produced in the hatchery may not be having all the nutrients required for the larvae, (especially the unsaturated fatty acids), the cultured Rotifer/Artemia are enriched with nutrient rich media and then fed to the larvae. Water Change Water quality in the rearing tanks is very important for The larvae are scooped gently using scoop net and better survival and growth of the larvae. Water provided transferred into buckets of known volume. After taking to the larval rearing tanks should be free from flagellates, random sample counting depending upon the number ciliates and other unwanted pathogenic organisms. Water required to be kept in the rearing tanks, larvae will be should be filtered through biological filters, pressure sand transferred to rearing tanks. filters. UV radiation treatment is also given, to get rid of Larval Stocking Density the pathogenic organisms. If chlorine treated water is drawn, residual chlorine should be removed, since, fish Freshly hatched healthy larvae (Hatchlings) from the larvae are highly sensitive to chlorine and water should incubation tanks are transferred carefully to the rearing be used only after de chlorination. 74 Central Marine Fisheries Research Institute From 14 - 23 December 2009 In the larval rearing tanks, the larvae stocked as well the assorted size rotifer can be given as feed. Artemia nauplii live feed supplied for the larvae will excrete nitrogenous are given as feed along with rotifers and green water from metabolites and other debris also will accumulate. They 9th day. By this time the larvae will be around 4 mm TL in have to be removed carefully. The debris and bottom size. Larvae can be feed exclusively with Artemia from sediment are removed by siphoning using siphon tubes. 16th day to 24th day. The density of the brine shrimp nauplii The bottom debris is slowly siphoned out along with water in the rearing medium is maintained at the rate 2000 nos./ into a trough with filter net. To maintain water quality in l initially and gradually increased to 6000/l as the rearing the larval rearing tanks, 30 – 40% water change is done days progress. The daily ration of Artemia nauplii feeding daily. The salinity should be maintained around 30 ppt. is adjusted after assessing the unfed Artemia in the rearing And the desirable range of temperature is 27 – 29 C. The tank at the time of water exchange and the larval density. 0 water level reduced (30 – 40%) in the rearing tank is leveled up with filtered quality seawater and green water after taking cell count of the algae in the rearing tank. Algal water is added daily up to 15 day. After bottom th cleaning and water reduction, while water change is done, algal water is also added depending upon the concentration, (around 20 thousand cells/ ml in the Feed density/quantity to be given to seabass By 21st day the larvae will be around 10 – 11 mm TL in size after completing larval development stages. From 25th day the larvae can be fed with Artemia sub adult (biomass) along with cooked minced fish/shrimp meat. The fry can also he weaned slowly to artificial feed. Algal water added should not be Under circumstances, when the rotifers could not be fed contaminated since in the open culture there is chance with marine Chlorella adequately, the nutritional quality of contamination by flagellates, ciliates and filamentous of such rotifers may be poor. In such case, the rotifers algae which will be toxic to the fish larvae. Apart from can be enriched with special enrichment media. being a source of feed for the rotifers in the tank, the Enrichment is done by keeping the rotifers in emulsified algae also help in the conversion of harmful excretory enrichment medium like SELCO DHA or cod-liver oil for products like ammonia and other metabolites in the 18 - 24 hours. By this process, the animals will ingest rearing container into less harmful nutrients. the enrichment media which is rich in Poly unsaturated rearing tank Fatty Acids (PUFA), required for larval growth. The animals Feeding are washed and fed to the larvae. In this way Rotifers Rotifer (Brachionus plicatilis) is given as feed to the larvae Artemia nauplii/ Artemia biomass can also be enriched from 3 day. Rotifer is maintained in the larval rearing and fed. Moina, a cladoceran can also be fed to the tanks at concentration at the rate 5 nos./ml initially. From seabass larvae after 21 days. rd 4 day to 15 day the rotifer concentration is increased th th to 10 – 20 nos./ml gradually. Every day after water Grading exchange, the food concentration in the tank should be Seabass while growing exhibits differential growth rate, assessed and fresh rotifers should be added to the required hierarchy, resulting different size groups in the same concentration. In the early stages (3 – 5 days) the larvae rearing tank. The large one’s shooters dominate others may not be in a position to ingest the large sized rotifers. for food and space and also prey on them. Seabass larvae Hence after collecting the rotifers from the tanks small are highly cannibalistic and it is more pronounced in early sized rotifer less than 1500 µm should be sieved using stages. In the rearing tanks, when the larval concentration suitable mesh size bolting cloth nets. . From 6 day is more and congregation takes place for food and feeding, th 75 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi the larger ones are tempted to feed on the smaller ones. Artemia biomass is seen, seabass fry are stocked at the To avoid this problem, regular grading has to be done. rate 800 – 1000 nos/m3. The pre-adult Artemia would The large sized larvae, (“Shooters”) have to be removed. form good food for seabass fry. The fry would not suffer Uniform sized larvae should be kept in the rearing tanks for want of food in the transitional nursery phase in the for better survival and growth. Grading should be done tank since the larvae are habituated to feed on Artemia th once in three days from 15 day or whenever different in the larval rearing phase. Along with ‘Artemia biomass’ size larvae are seen in the tanks. Grading can be done available as feed inside the tank supplementary feed using a series of fish graders with different pore size of 2 mainly minced fish/shrimp meat is passes through a mesh mm, 4 mm, 6 mm, 8 mm, 10 mm. When the larvae are net to make each particle of size of around 3 – 5 mm and allowed to pass through the graders, different size will be cladocerans like Moina sp can also be given. The fish/ retained according to pore size of the sieves. Grading shrimp meat feeding has to be done daily 3 – 4 times. may cause injuries leading to mortality. Hence proper Feeding rate is 100% of the body weight in the first week care should be taken in handling the larvae. Prophylactic of rearing. This is gradually reduced to 80%, 60%, 40% treatment with 5 ppm Acriflavin can be given. By adopting and 20% during 2nd, 3rd, 4th and 5th week respectively. these practices survival rate up to 48% has been achieved Regular water change to an extent of 70% is to be done with average survival rate of around 15 % in 25 days in daily. The left over feed and the metabolites have to be larval rearing phase. After rearing the larvae in the removed daily and aeration should be provided. In a rearing hatchery for 25 – 30 days the fry can be transferred to period of 4-5 weeks in the nursery rearing, the seed will nurseries for further growing. be in the size of 1.5 to 3.0 g/ 4-6 cm with survival rate of Nursery rearing 60-70%. Adopting this technique at a stocking density at the rate 1000 nos/m3 in the hatchery, survival rate up Nursery Rearing in Hatcheries to 80% has been achieved. For the better survival during Seabass fry of 25 – 30 days old in the size of 1.0 – 1.5 cm early growth phase, regular Grading should be done. can be stocked in the nursery tanks of 5 – 10 tonn capacity Vessels/trough placed with different mesh sized nets can circular or rectangular (RCC or FRP) tanks. Outdoor tanks be used for grading. When the seed are left into the are preferable. The tanks should have water inlet and containers the seeds will be sieved in different grades outlet provision. Flow through provision is desirable. In according to the mesh size and seed size. Care should be situ biological filter outside the rearing tanks would help taken that the fry are not injured while handling. If the in the maintenance of water quality. The water level in number is less it could be manually done. the rearing tanks should be 70 – 80 cms. Good aeration facility should be provided in the nursery tanks. After Status of seabass farming filling with water 30 – 40 cm and fertilized with Amongst the cultivable fishes in India, Seabass fetches ammonium sulphate, urea and superphosphate at the rate higher price in domestic market varying between Rs.100- 50, 5 and 5 gm (10: 1 : 1 ratio) per 10 tonne of water 250 per kg depending upon the size, the availability and respectively. The natural algal growth would appear within season. It is extensively cultured, in South East Asian 2-4 days. In these tanks freshly hatched Artemia nauplli Countries like Thailand, Malaysia, Singapore and Australia. at the rate 500 – 1000 l are stocked after leveling the Culture of seabass is relatively easy and dependable with water to 70 – 80 cm. The nauplii stocked are allowed to fewer risks. Based on case studies, in Thailand it has been grow into biomass feeding with rice bran. When sufficient estimated that the production of seabass culture was 20.5 76 Central Marine Fisheries Research Institute From 14 - 23 December 2009 kg/m3. The price of seabass is US$2.27 per kg. The total Aquaculturists. With the advances in the technology in income from the cage is US $ 46.49 per m . The rearing the production of seed under captivity assuring the supply cost is US $ 24.15. The net return is US $ 22.34 per m . of uniform sized seed for stocking and quality feed for In the culture operation the fixed cost in cage culture is feeding, the seabass culture is done in South East Asian only 5.9%. The variable costs such as feed, seed, labour Countries and Australia in more organized manner. The etc cost 94.1%. The feed alone costs 63%, followed by major problem in the development of seabass aquaculture the seed cost. Seabass, the value added finfish can be in India is the availability of seed in adequate quantity considered as a complementary to shrimp for the and the time of need and quality feed for nursery rearing sustainability of brackishwater aquaculture. and grow out culture. The former has been overcome 2 3 Traditional Culture and the technology package for the seed production of seabass under controlled conditions is available. The Seabass is cultured in the ponds traditionally as an suitable feed for the culture of seabass is being developed. extensive type culture throughout the areas in the Indo- The seed production technology developed by CIBA has pacific region where seabass is distributed. In low lying already been commercialized and the feed technology will excavated ponds, whenever the seabass juveniles are be ready shortly for commercialisation. available in the wild seed collection centers (For eg. April technological improvements in the seabass culture have June in West Bengal, May-August in Andhra Pradesh, motivated the farmers to select seabass as a candidate Sept-Nov. in Tamil Nadu, May to July in Kerala and June- species for aquaculture. Farmers have been adopting July in Maharashtra. Juveniles of assorted size seabass improved farming practices in seabass culture. These are collected and introduced into the traditional ponds which will be already with some species of fish, shrimps Improved Seabass Culture Methods and prawns. These ponds will have the water source from The traditional culture method is improved with stocking adjoining brackishwater or freshwater canals, or from of uniform sized seed at specific density and fed with low monsoon flood. The juvenile seabass introduced in the cost trash fishes/formulated feed of required quantity. pond will prey upon the available fish or shrimp juveniles Water quality is maintained with exchange periodically. as much as available and grow. Since, seabass by nature Fishes are allowed to grow to marketable size, harvested is a species with differential growth are introduced into and marketed for high unit price. Seabass culture can be the pond at times of food scarce, the larger may resort to done in more organized manner as a small-scale/large feed upon the smaller ones reducing the number. Seabass scale aquaculture in brackishwater and freshwater ponds are allowed to grow for 6-7 months of culture period till in cages. such time water level is available in these ponds and then harvested. At the time of harvesting there will be large fish of 4 to 5 kgs as well as very small fishes. In this manner production up to 2 ton/ha/7-8 months have been obtained depending upon the number and size of the fishes entered/introduced into the pond and the feed available in the pond. Polyculture This is an improvement over the traditional method, where the feed, the live fishes, shrimps are deliberately allowed in to the seabass culture ponds to serve as facilitating feed for the seabass in the pond. In the traditional method there is no control over the quantity and quality of the However, this practice is highly unorganized and without feed entering the ponds which may or may not be any guarantee on production or return for the adequate. At times of scarcity for feed, the seabass may 77 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi resort to cannibalism resulting in low survival and Floating cages: The net cages are attached to wooden production though few fishes will be large size. Under frames kept afloat using plastic drums. Anchors or polyculture method, the feed in the form of forage fishes Concrete weight blocks as anchors can be attached to are produced in the culture ponds itself and made available the corners of the net cage at the bottom. These types to the seabass fish to prey upon as and when it requires. of cages can be installed in areas with water depth more Grow out culture of seabass in cages Fish culture in cages has been identified as one of the eco-friendly at the same time intensive culture practice for increasing in fish production. Cages can be installed in open sea or in coastal area. The former is yet to be developed in many countries where seabass is cultured but coastal cage culture is an established household activity in the South East Asian countries. There are than 4 meters with feeble water current. Stationary cages: These are fixed enclosures, which can be installed, in shallow water areas in lagoons, brackishwater lakes having water depth of 2-4 meters. The cage net is fastened to wooden poles erected in the water system at the four corners. Stocking Density abundant potential as in India also for cage culture in the In the cages, fishes can be stocked at the rate 25-30nos/ lagoons, protected coastal areas, estuaries and Creeks. m3 initially when they are in the size of 10-15 gm. As Since, cage culture of seabass has been proved to be a they grow, after 2-3 months culture, when they are around technically feasible and viable proposition this can be 100-150 g stocking density has to be reduced to 10-12 taken up in a large scale in suitable areas. nos/m3 for space. Cage culture is normally done in two phase – till they attain 100-150 gms size in 2-3 months Cage culture system allows high stocking density, assures and afterwards till they attain 600-800 in 5 months. high survival rate. It is natural and eco-friendly and can be adapted to any scale. Feeding can be controlled and Feeding in Cage cages can be easily managed. Harvesting is not expensive. Fishes in the cage can be fed with either extruded pellets Water depth and water current alone the criteria. Even or with low cost fishes as per the availability and cost. in areas, where the topography of the bottom is unsuitable Floating pellets have advantages of procurement, storage for pond construction, cage can be installed. Diseases and feeding. Since, a lot of low cost fishes are landed in can be easily monitored. Fishes in the cages can be the commercial landings in the coastal areas which are harvested as per the requirement of the consumers, which fetching around Rs.3-5/kg only used as feed for seabass will fetch high unit price. Above all, cage culture has got culture. Low cost fishes like Tilapia available in the low capital input and operating costs are minimal. Cages freshwater and brackishwater also serve as feed for can be relocated whenever necessary to avoid any seabass in ponds and in many cage culture operations. unfavorable condition. The rate of feeding can be maintained around 20% initially Design of Cages and reduced 10% and 5% gradually in the case of trash Grow out cages of 20 or 50 m2 are preferable for easy management and maintenance. Cages are fabricated with polyethylene netting with mesh size ranging from 2 to 8 fish feeding and in the pellet feeding, the feeding rate can be around 5% initially and gradually reduced to 2-3% at later stage. cm depending upon juvenile fish propose to stocked in In the feeding of low cost fish FCR works out around 6 or the cages. There are two types of cages: 7 (i.e. 7 kg of cheaper fishes has to be given for one kg of 78 Central Marine Fisheries Research Institute From 14 - 23 December 2009 seabass). In the case pelleted feeding FCR is claimed to be around 1 to 1.2 in Australia. However, the cost effectiveness of the pellet feeding for seabass in grow out culture has to be tested. Cage farming in India can be taken up in pilot scale by utilizing different ecosystem. Cost effectiveness of seabass cage farming with formulated feed in high density in the marine water ecosystem has to be evaluated. The Cage Management Since cages are inside the water and exposed to water current, the debris materials drifted may adhere to the cages and clog the mesh restricting the water exchange. The fouling organism will also attach and clog the meshes. Other animals like Crab may damage the nets. The cages should be regularly checked for clogs and leaks. Damaged nets should be repaired or replaced. Conclusion The clogging will reduce water exchange, and lead to accumulation of waste products depleting the oxygen causing stress to the fishes, affecting feeding and growth. If the damage is not repaired immediately, the fishes will escape from the cages. Production Under cage culture, since seabass can be intensively stocked and properly managed, the production will be high. Frequently culling and maintenance of uniform sized fishes in to the cages will ensure uniform growth and high production. Production of 6-8 kg/m2 is possible in the cages, under normal maintenance and production as high as 20-25 kg/m2 is obtained in intensive cage management in the culture of seabass. Integration of cage culture of seabass with shrimp culture If seabass can be weaned to feed on floating pellets, because of their addictive nature to selective feed, they will not resort to prey upon shrimp as normally experienced in shrimp culture ponds. If the water depth can be maintained around 1.5-2.0 m, in a pond, cages can be installed in the shrimp culture pond itself and seabass seed weaned to feed on floating pellets can be stocked in the cages and reared. In this way, seabass culture will be a complimentary to shrimp culture. production of value added species like seabass will be increased by using marine and freshwater reservoir cage system. There is need of creation of infrastructure facilities to carry out the nursery rearing and cage farming of the seabass. The safety and security of the stock has to be assured since the fisheries in marine water are prone to poaching. The value and importance of the cage farming has to be taken as massive awareness programme in the surrounding areas. The programme can be initiated as a community programme through fishermen/women cooperatives. Further Reading A book on simplified hatchery technology for seabass, Lates calcarifer seed production (2006). Central Institute of Brackishwater Aquaculture, Chennai, India A.R.T.Arasu, M.Kailsam, J.K.Sundaray, M. Abraham, R.Suburaj, G.Thiagrajan & K.Karaiyan. Arasu, A.R.T., M. Natarajan, M. Kailasam and J K Sundaray (2008). Induced breeding techniques in Brackishwater Fin Fishes. Pp7-14 in the proceedings of National Seminar on Recent Trends in Aquaculture Biotechnology held at Jamal Mohamed College, Tiruchirapalli, Tamil Nadu sponsored by University Grant Commission., August 2008. Asian Seabass fish seed Production and culture. (2009) CIBA special publication No-42, Edited by A.R.T. Arasu, M. Kailasam & J K Sundaray Biswas, G., A. R. Thirunavukkarasu, J. K. Sundaray and M. Kailasam (2008). Effect of stocking density on the growth dispersion in Asian seabass Lates calcarifer (BLOCH) under nursery rearing presented in the 8th Indian Fisheries Forum held on 22nd to 26th November 2008 at CIFRI, Barrackpore, Kolkata. .Arasu, A.R.T, M, Kailasam, J.K.Sundaray, R.Subburaj, G.Thiagarajan and K.Karaiyan. Improved hatchery technology for Asian seabass Lates calcarifer (Bloch) (2008). CIBA special publication No.34. pp 1-38 79 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Sundaray, J.K., A.R.T.Arasu, M. Kailasam and G. Biswas (2008). Reproductive hormones in fishes in the proceedings of National Seminar on Recent Trends in Aquaculture Biotechnology held at Jamal Mohamed College, Tiruchirapalli, Tamil Nadu sponsored by University Grant Commission., pp.15-21, August 2008. Kailasam, M., Thirunavukkarasu A.R, Selvaraj,S and P.Stalin 2007. Effect of delayed initial feeding on growth and survival of Asian seabass Lates calcarifer (Bloch). Aquaculture 271 (2007) 298-306 Kailasam, M., A.R.Thirunavukkarasu, J.K.Sundaray, Mathew Abraham, R.Subburaj, G.Thiagarajan and K.Karaiyan 2006. Evaluation of different feeds for nursery rearing of Asian sea bass Lates calcarifer (Bloch) Indian Journal of Fisheries 53 (2): 185-190. 80 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Importance of water quality in marine life cage culture Prema, D. Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India premadicar@gmail.com Water quality in marine life cage culture is one of the most important factors that determine production and mortality. Choice of site for marine cage culture is of paramount importance since; it not only affects water quality but also greatly influences the economic viability. Once the site is selected for marine cage culture, there is little that can be done to improve the site, if water exchange is poor. Criteria for selecting a site for marine cage culture Environmental Criteria Wind The wind can determine the suitability of a particular site or area for cage fish culture through its influence on cage structures and caged stock. Of particular concerns are violent storms. But up to certain level, effects due to moderate winds can be profitable by the mixing of water. Maximum permissible wind limit is 30 – 40 km hr-1. The wind velocity limit also emphasis the need of suitable season for marine cage culture when wind velocity is low. The cage culture of sea bass conducted by CMFRI, Cochin was during October – April in the open sea, at Munambam, Depth off Cochin. In the Arabian sea, during June – August, the Shallow bays with limited depth of water under cages are winds blow at their greatest strength and by September, not favorable for water renewal and generally the settling the wind velocity decreases and by October – November, of wastes. A depth of 10 – 30m at low tide may be the wind starts blowing from north westerly to north considered as ideal condition. Cages should be sited in easterly with comparatively low velocities. sufficient depth to maximize the exchange of water, yet keep the cage bottom well above the substrate in order to Waves avoid interaction between the cage bottom and sea floor. Wind driven waves are propagated by the frictional drag Water is drawn into the cage not only through the sides of wind by the wind blowing across a stretch of water but also through the bottom panel and as the cage bottom that transfers energy to the fluid. Wave size is determined approaches the substrate, flows become increasingly by wind velocity, wind duration and the distance of open, impeded. It can cause chemical and bacterial interactions, unobstructed water across which the wind blows; and is net damage and predation of the fish by crab and bottom also influenced by the waves present when the wind starts organisms. The cage of sea bass established by CMFRI, to blow. At the windward end, waves are poorly developed Cochin was at a depth of 10 m in inshore area off Cochin. with small wave heights and short periods of oscillation. 81 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi However, waves develop with distance, reaching maximum size when they attain the same velocity as the wind. Wave height increases with wind velocity and wave energy increases proportionally with square of wave height. The maximum limit of wave height for working on floating cages is 1m. Substrate The cage site substrate range from rocky to soft mud. Mud or rock bottom may cause difficulties for a safe and reliable anchorage for cage. A sandy or gravel bottom is generally looked for. Currents and tide Water Quality Criteria Good water exchange through cages is essential both for Temperature and salinity replenishment of oxygen and removal of waste metabolites. A weak and continuous current stream is favorable to bring oxygen and remove wastes in a cage. However excessive currents impose additional dynamic loadings damaging floating structures or cages, reduce the cage usable volume due to the deformations of the net and may adversely affect fish behavior. The limit for current velocity is with a minimum of 0.05 m S-1 to a maximum of 1 m S-1. Fish and other farmed organisms have no means of controlling body temperature, which changes with that of environment. A rise in temperature increases metabolic rate and causes a concomitant increase in oxygen consumption and activity as well as production of ammonia and carbon dioxide. Salinity is a measure of the amount of dissolved solids present in water and is usually expressed in parts per thousand. Its relevance to cage culture lies principally in its control of osmotic In all except a few coastal regions of the world, tidal pressure, which greatly affects the ionic balance of currents are the predominant source of surface water aquatic animals. Rapidly fluctuating conditions of currents. Attractive forces exerted by the moon and sun temperature and salinities are harmful for marine life on the Earth produce tidal waves. The crest and trough of cage culture. Seasonal changes are also to be taken care the wave are termed high and low tide respectively, while of during the culture period. For most tropical marine the wave height is referred to as the tidal range. Associated life aquaculture, a temperature of 26 - 28ºC in early with the rise and fall of the tide are the horizontal motions morning with no abrupt changes is considered as of water or tidal currents. Maximum current velocity occur suitable. Similarly preferred salinity range is 25 – 40 ppt, at the middle of the rise (flood) and fall (ebb) ie., during evading abrupt changes. the mid time between highest and lowest tide. For marine cage culture, limited tide amplitude (<1m) is preferred. Dissolved Oxygen Based on the tide table for the particular area of the coast, Dissolved oxygen is required by all higher marine current velocity thus can be predicted in pre-monsoon organisms for the production of energy for essential and post-monsoon season during a cage culture period. functions such as digestion and assimilation of food, But in monsoon, current velocity is unpredictable. Current maintenance of osmotic balance and activity. Oxygen velocity during monsoon is mainly influenced by littoral requirements vary with species, stage of development, current, strong winds, wave effects and increased river size and are also influenced by environmental factors such discharge. Hence there is every chance that current as temperature. If the supply of oxygen deviates from the velocity can exceed its permissible maximum limit ideal feeding, food conversion, growth and health can be prescribed for marine cage culture. Monsoon season is adversely affected. It is therefore important that good generally avoided for marine cage culture activity. oxygen conditions prevail at a site. 82 Central Marine Fisheries Research Institute From 14 - 23 December 2009 During the day, there is a net production of oxygen, but at ranging in size from colloidal to coarse dispersions. Turbid night, when photosynthesis stops, the algal community in conditions arise from organic or inorganic solids suspended water becomes a net oxygen consumer. Where there are in the water column as a result of soil erosion, mining large algal communities, super saturation of DO may occur wastes and other industrial effluents. Cage fish farms are during the day and sub saturation condition prevail at night, themselves a source of suspended solids. with late afternoon maxima and pre-dawn minima, stressing fish. The environmental conditions conducive to blooms usually occur during the warmer months in areas subject to high nutrient influxes. External sources such as sewage discharges and agricultural run off may be important contributors. However, a sudden upwelling of nutrient rich water from deeper layers of the water body during the break down of stratification may also stimulate blooms. Problems can occur when algal blooms die. During decomposition, microbial respiration may remove much or even the entire DO resulting in fish kills. Benthic oxygen demand can cause de-oxygenation of the hypolimnion. Good mixing, water exchange and flushing by proper currents, tides and winds is a must in order to shun this situation. Marine sites which have good bottom current which disperse settling wastes are desirable. Preferred DO level for marine life culture is >6 mg l-1. The quantity and quality of material suspended in water column at any particular moment is largely determined by water movement, which transports, fractionates and modifies solids. Large, dense particles are more easily settled than small, less dense particles. Water currents can also prevent particles from settling and re-suspend settled materials. Water chemistry and salinity in particular influences turbidity through its effect on flocculation and settling and is important in the transport of sediments. High levels of suspended solids cause gill damage, inducing the gill epithelial tissues to proliferate and thicken. If damage is sufficiently severe, the fish will die. Turbidity levels less than 100 mg l-1 have little effect on most species. However, duration of exposure is important. Preferred range of dry suspended matter for marine life cage culture is <2 mg l-1. pH pH is a measure of hydrogen ion concentration of a Color / Transparency solution. pH is important to aquatic life because extreme Part of the light (solar radiation) striking water does not values of it can damage gill surfaces, leading to death penetrate the surface. A portion is reflected depending and because it affects the toxicity of several common on the roughness of the water surface and the angle of pollutants like ammonia and heavy metals. radiation. As light passes through water, scattering and differential absorption by the water takes place. Turbidity The pH of sea water usually lies in the range 7.5 – 8.5. Sea and color in water may result from colloidal clay particles, water is also well buffered ie., comparatively resistant to from colloidal or dissolved organic matter or from an changes in pH through the addition of alkaline or acidic abundance of plankton. Secchi disk visibility can be taken compounds. Preferred pH for marine life culture is 7.8 – 8.4. as a measure of colour / transparency of the water in Turbidity marine life cage culture. The Secchi disk is a weighted Total suspended solids disk, 20 cm in diameter and painted in alternate black and white quadrants. The average of depths at which the Turbidity refers to the decreased ability of water to disk disappears and reappears is the Secchi disk visibility. transmit light caused by suspended particulate matter Optimum transparency expressed as Secchi disk visibility 83 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi for marine culture is <5 m as yearly mean. Transparency growth. Preferred range of Ammonia N as (NH4 + NH3) is an important factor deciding light penetration and for marine culture is < 0.1 mg l-1. euphotic zone (the stratum of water receiving 1% or more of incident radiation, where, photosynthesis proceeds at Nitrite N rates exceeding respiration), affecting the primary Nitrite originates as an intermediary product of productivity and oxygenation of the culture water. nitrification of ammoniacal N by aerobic bacteria. Marine water has high concentration of calcium and chloride Total inorganic nitrogen Ammonia N Ammonia is the most toxic form of inorganic N produced in water. The major source of ammonia in water is the direct excretion of ammonia by fish. It also originates from the mineralization of organic matter by heterotrophic which tend to reduce nitrite toxicity. Nitrate N Nitrate is the end product of nitrification of ammoniacal nitrogen by aerobic autotrophs. Its presence can also be due to land drainage. bacteria and as a by product of nitrogen metabolism by The total inorganic nitrogen for marine life culture is < most aquatic animals. Both ammonia (NH 3 ) and 0.1 mg l-1. ammonium (NH4+) are toxic, but NH3 is much more toxic than NH4+. Ammonia toxicity increases with the increase Total inorganic phosphorus in pH and temperature. Phosphorus (P) is found in the form of inorganic and The ammoniacal N content of water is an index of the organic phosphates (PO4) in natural waters. Inorganic degree of pllution. Its concentration in unpolluted water should never be more than 0.1 mg l-1 and below this level, healthy growth of fish is expected. Aquatic autotrophs rapidly utilize ammonium ions, thus naturally preventing it from reducing to toxic levels. As ammonia concentration increases in water, ammonia excretion by fish decreases and levels of ammonia in blood and other tissues increase. This results in an elevation of phosphates include orthophosphate and polyphosphate while organic forms are those organically-bound phosphates. Phosphorous is a limiting nutrient needed for the growth of all plants - aquatic plants and algae alike. However, excess concentrations of P can result to algal blooms. The total inorganic phosphorus for marine life culture is < 0.015 mg l-1. COD (Chemical Oxygen Demand) blood pH and adverse effects on enzyme catalyzed The COD of water represents the amount of oxygen reactions and membrane stability. High ammonia required to oxidize all the organic matter, both concentrations in water also affect the permeability of biodegradable and non biodegradable by a strong chemical fish by water and reduce internal ion concentrations. oxidant. Preferred Chemical Oxygen Demand for marine Ammonia also increases oxygen consumption by tissues, life culture is < 1 mg l-1. damages gills and reduces the ability of blood to transport oxygen. Histological changes occur in kidneys, spleen, Chlorine thyroid and blood of fish exposed to sub-lethal Both free and combined, residual available chlorine are concentrations of ammonia. Chronic exposure to extremely toxic to fish. The measurable concentrations of ammonia increases susceptibility to diseases and reduces chlorine in water for marine life culture is <0.02 mg l-1. 84 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Heavy metals anthropogenic sources. Anthropogenic sources of copper They originate mainly from anthropogenic industrial pollution. The toxicity of heavy metals is related to the dissolved ionic form of the metal rather than total concentration of the metal. in the environment include corrosion of brass and copper pipes by acidic waters, industrial effluents and fallout, sewage effluents, and the use of copper compounds such as copper sulphate as aquatic algicides. Major industrial sources of copper include smelting and refining industries, copper wire mills, electroplating, metal finishing, coal Mercury Mercury (Hg) is toxic to both aquatic life and humans. Inorganic form occurs naturally in rocks and soils. It is being transported to the surface water through erosion and weathering. However, higher concentrations can be burning, and iron and steel producing industries. Large quantities of copper can enter surface waters, particularly acidic mine drainage waters, as a result of metallurgical processes and mining operations. found in areas near the industries. The most common The toxicity of copper to marine organisms in marine and sources are caustic soda, fossil fuel combustion, paint, estuarine environments is influenced by physical factors pulp and paper, batteries, dental amalgam and and chemical characteristics of the marine environment: bactericides. The copper in water for marine life culture should be <0.02 Mercury remains in its inorganic form (which is less toxic) until the environment becomes favorable, i.e. low pH, low dissolved oxygen, and high organic matter where some mg l-1. Pesticides of them are converted into methylmercury (the more toxic Pesticide refers to any chemical used to control unwanted organic form). Methylmercury tends to accumulate in the non-pathogenic organisms, including insecticides, fish tissue, thus making the fishes unsafe to eat. acaricides, herbicides, fungicides, algicides and rotenone (used in killing unwanted fish) (Svobodova, 1993). These The total mercury in water for marine life culture should chemicals are designed to be toxic and persistent, thus it be <0.05 mg l . is also of concern in aquaculture. It can affect the quality -1 of the aquaculture product as well as the health of the Lead Lead (Pb) comes from deposition of exhaust from vehicles in the atmosphere, batteries, waste from lead ore mines, lead smelters and sewage discharge. Its toxicity is dependent on pH level, hardness and alkalinity of the water. The toxic effect on fish is increased at lower pH level, low alkalinity and low solubility in hard water. fish and humans. Pesticide can be split into seven main categories namely, inorganic, organophosphorous, carbamates, derivatives of phenoxyacetic acid, urea, pyridinium, and derivatives of triazine (Dojlido and Best, 1993). Among these, the chlorinated form is of particular concern due to its persistence and tendency to bioaccumulate in fish and The lead in water for marine life culture should be <0.1 shellfish. Some examples are dichloro-diphenyl-trichloro- mg l-1. ethane (DDT), aldrin, dieldrin, heptachlor, and chlordane. The most common sources are agricultural run-offs, Copper effluents from pesticide industries and aquaculture farms. Copper enters the environment naturally through the The safe level of DDT group in water for marine life culture weathering and solution of copper minerals and from should be < 0.025 µg l-1. 85 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Dojlido, J., and G. A. Best. 1993. Chemistry of Water and Water Pollution. West Sussex: Ellis Horwood Limited. Rao, P.C.V.K. ., Kumar, P.V.H and Kumar, M. 1996. Pre-monsoon current structure in the shelf waters off Cochin : In. Proceedings of the Second Workshop on Scientific Results of FORV Sagar Sampada. V.K. Pillai et al. eds. Department of Ocean Develpoment, Govt. of India, New Delhi.pp. 1924. Masser, P. Michael. 1997. Cage culture – site selection and water quality. Southern Regional Aquaculture Centre Publication No. 161. Svobodová, Z., R. L., J. Máchová, and B. Vykusová. 1993. Water Quality and Fish Health. EIFAC Technical Paper no. 54. Rome: FAO. References Beveridge, M. 2004. Cage Aquaculture. Blackwell Publishing. Third Edition. pp.111-158. 86 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Diseases of seabass in cage culture and control measures Sobhana, K. S. Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India sobhana_pradeep@yahoo.co.in The cage culture of finfish, especially marine cage farming is Diseases in Cage fish farming becoming more popular because of the many economic The disease types and severity are greatly influenced by advantages associated with it. Though, operationally this has the species of fish, the conditions in which the animals a number of advantages, the practice is vulnerable to natural are cultured and the husbandry management. Fish hazards and can be affected by occurrence of diseases. cultured in floating cages become particularly susceptible Disease outbreaks can occur more often when fish are raised to disease when various environmental parameters such under intensive culture conditions and can pose problems in as temperature, salinity, dissolved oxygen and suspended cage culture. Increased production under high density can particles fluctuate suddenly or widely, or following rough, create conditions conducive to outbreaks of infectious although often unavoidable, handling operations. Once diseases and an increase in prevalence of parasites. Infectious conditions suitable for pathological changes develop, diseases in fish culture are not only augmented by waste progress to disease in the warm water environment is pollution, but exacerbated by crowding, handling, rapid. Early detection of behavioral changes and clinical temperature and biofouling. The most common fish disease signs in the cultured animals are critical for proper in cages is vibriosis caused by Vibrio spp. Furthermore, diagnosis of the disease. In addition to diseases caused abrasions cause fin and skin damage to cultured stocks. by infectious agents, diseases and abnormalities due to Occurrence of infection/disease may be minimized by environmental stresses and nutritional deficiencies have selecting good sites, proper mooring and observance of also been recognized, which can lead to secondary optimal stocking densities and careful handling of stocks. infections. Certain types of physical injury are specific Disease monitoring Monitoring of fish stock health is essential and early indications can often be surmised from changes in behaviour, especially during feeding. Some indication of disease status can be gained from examination of moribund fish netted from the cage surface. Rapid to caged fish, e.g., if over-stocked they may suffer from fin and skin damage caused by net abrasion and are susceptible to pathogenic organisms if handled without due care. Caged marine fish are vulnerable to “red boil disease” (Vibrio anguillarum) following routine handling operations at polluted sites (Chua and Teng, 1980). detection and removal of dead fish helps to prevent the Caged fish established in coastal environments may be spread of disease. exposed to a wide range of pathogens. From this 87 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi perspective, the worst sites are those in which pathogenic or potentially pathogenic organisms exist prior to establishment of the farm and those in which disease organisms thrive following the installation of cages. Facultative pathogenic organisms are often associated with water bodies where a source of infection, such as untreated sewage, is present. There exists a link between trophic state and bacterial/fungal infections in fish. Chua (1979) observed that the ectoparasitic isopod Nerocilia sp. that attacked caged rabbit fish (Siganus rivulatus) was more prevalent in organically enriched waters. Infectious diseases of cage cultured fish Generally, infectious diseases of fish are caused by virus, bacteria, fungi and parasites. Diseases caused by viruses Viral diseases have not been considered to be a significant factor in marine and brackishwater culture. However, such disease as lymphocystis has recently become one of the problems in seabass culture. Viral diseases in cage cultured fish have been on the increase since the 1980’s in East Asia and the 1990’s on south-east Asia (Nakai, Both wild fish populations and intermediate hosts in the 1995). Virological research received a new impetus life cycle of a fish parasite represent a risk for the fish following the high mortality in hatchery-bred juvenile fish farmer. Cages of salmon attract scavenging sathe soon after being placed in sea cages. With the increasing (Pollachius virens ) that often harbour the sea lice awareness of virus-related diseases and with new species Lepeophtheirus salmonis and Caligus elongatus, and of fish being selected for culture, more reports of known laboratory trials have clearly shown that lice can transfer and new viral diseases are to be expected. between host species (Bruno and Stone, 1990). In the UK, caged fish were found severely infested with the Viral nervous necrosis (VNN) cestodes, Triaenophorus nodulosus and Diphyllobothrium VNN disease has been found in all warm water marine spp. resulting in heavy mortalities and the closure of at environments where marine fish have been cultured in least one farm (Wootten, 1979; Jarrams et al., 1980). The cage environments, particularly in juvenile stages. The viral source of infection was subsequently traced to the wild particles are packed in the cytoplasm of retinal and brain fish populations. cells of affected fish. Infected fish exhibit whirling Disease risks can be minimized by avoiding sites where a pre-development survey reveals parasites or disease agents to be present in the wild fish or intermediary hosts. However, problems may still occur through the introduction of diseased stock to the farm or the attraction of birds and other opportunistic predators. Epidemiological studies have revealed the importance of management in reducing the incidence of disease and mortality. A four year study of disease outbreaks in 11 Irish salmon farms showed that interruption of parasite movements, lethargy, dark body colouration, loss of balance and hyper-excitability in response to noise and light. Mortalities are usually high and occur within a week of the onset of first signs. Extensive spongiosis is typically observed in the retina, brain and central nervous system. VNNV is an RNA virus and can be detected by RT-PCR. A PCR method based on the sequence of the virus coat protein genome (RNA2) was used to diagnose the virus in spawners, suggesting vertical transmission of the infection. life cycles through fallowing, the separation of year classes At present there is no known method of therapy, but of fish to different sites and the practice of basic hygiene vaccination using recombinant coat protein of live piscine methods could significantly reduce the severity of disease nodavirus in sevenband grouper, Epinephelus outbreaks (Wheatley et al., 1995). septemfasciatus, resulted in significantly lower mortality 88 Central Marine Fisheries Research Institute From 14 - 23 December 2009 in the virus challenge tests, indicating great potential for environmental conditions. In south-east Asia, trash fish protection against the virus. used as feed may be another source of infection. A decrease in stocking density and culling of visibly infected Iridoviral disease individuals are the only known measures that can be Iridoviral disease has been reported in more than 20 adopted to reduce the impact of the disease. marine species, from south-east and east Asia. Affected fish become lethargic and severely anaemic. The gills are Diseases caused by bacteria hemorrhagic, the spleen is heypertrophic and the iridovirus Many clinical signs of bacterial diseases of cultured marine appears in a crystalline array in the enlarged, basophilic fish are similar. Definitive diagnosis requires the isolation splenic cells. Presumptive diagnosis based on Giemsa and in vitro culture of the organisms involved. A great staining of histological sections can be confirmed by number of aquatic bacteria are opportunistic and under immunoflorescence or by PCR assay. normal environmental conditions do not cause disease, An experimental vaccine prepared by Nakajima et al. (1997) produced a higher survival in treated red seabream than in control group, suggesting the possibility of controlling the disease through vaccination. Lymphocystis disease Lymphocystis disease is commonly found in seabass raised in cages especially among juveniles. It has been observed at all temperatures in rather high salinity. Lymphocystis is a highly contagious infection and the disease follows a chronic course and, in general mortalities are limited. The infected fishes recover within a few weeks of the onset of the outbreak displaying little or no scar tissue. Although known to infect 30 families of marine fish, in south-east Asia, only Asian sea bass has been reported to be affected by this disease. becoming pathogenic only when the balance of the host/ environment is changed by elevated stocking densities, inadequate nutrition, deteriorating water quality, rough handling (e.g., net changing, grading) and other stress factors. Gram-negative bacteria Vibriosis is the disease caused by a group of bacteria belonging to the family Vibrionaceae. Vibrios are ubiquitous in all marine environments and most are facultative pathogens. The infectious disease they cause is one of the most significant in mariculture. Diseases caused by Vibrio sp. typically appear as ulcerative haemorrhagic septecaemia. It occurs frequently during periods of fluctuations in salinity, increased organic load, or stress brought on by net changing and grading of fish. The period following initial stocking is particularly critical. The disease is characterized by tumour-like masses of The clinical signs are congestion and red boils appearing tissue on the body surface. These growths are clusters of on the body surface and gradual darkening of the body. extremely hypertrophic fibroblastic dermal cells. The petechial haemorrhages usually enlarge into irregular Occasionally internal organs can become infected. and deep lesions, which disintegrate the skin, exposing Diagnosis of lymphocystis disease is confirmed through the underlying muscle, which becomes necrotic. The histological sections and appropriate staining of the tissue tissues surrounding the infected vent are usually reddened lesions. The observation of the typical icosahedral virions and inflamed. The body is completely covered by a thick by electron microscopy offers further confirmation. layer of mucus. Internally, there is congestion and Horizontal transmission is the most probable route, hemorrhage of the liver, spleen and kidney, frequently facilitated by high stocking density and unfavorable accompanied by the presence of necrotic lesions. The gut 89 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi and particularly the rectum may be distended and filled It is difficult to prevent and control the disease in the with a clear viscous fluid. cage environment. The standard treatment is feed The pathogenic vibrios which have been isolated from seabass include Vibrio parahaemolyticus, V. anguillarum and V. alginolyticus. Good husbandry practices and adequate nutrition are essential to prevent the development of vibriosis. Though in the initial stages the medicated with oxytetracycline or a bath in sodium nifurstyrinate. However, the results are usually unsatisfactory. A combination of freshwater treatment and reduction of stocking density helps to reduce mortality in affected seabass. disease can be effectively treated with antibiotics, the Tenacibaculum maritimum (formerly Flexibacter use is not recommended due to the risk of development maritimus ) is reported as the etiological agent of of resistant strains. Prophylactic measures such as flexibacteriosis disease in red seabream (Pargus major), vaccines are recommended. European seabass, Dicentrarchus labrax etc. Pasteurellosis – Photobacterium damsela Gram-positive bacteria Pasteurellosis is an most important bacterial disease of cultured maine fish which is caused by the Gram-negative Streptococcosis non-motile bacterium, Photobacterium damsela. This is Streptococcosis caused by non-motile, gram-positive a septicaemic disease with no external signs except bacteria, Streptococcus sp. is most severe when farmed occasional darkened spots on the body surface. A large fish are stressed and water temperature is high. The onset number of white spots corresponding to foci of bacterial of the disease is related to the rapid growth of the colonization engulfed by phagocytes are found in the bacterium in the intestine where both extracellular and spleen and kidney, and to a lesser extent in the liver. The intracellular toxins are produced. The common clinical diseased fish rapidly lose their vigour, sink to the bottom signs are darkening of the body, erratic swimming, of the cage and die. Ampicillin and florfenicol have been hemorrhage in the intestine, liver, spleen, and kidney and reported to be effective when administered in feed. abdominal distention. Necroses of the heart, gill, skin and However, this bacterium is known to become resistant eye have also been reported. to antibiotics. Vaccine preparations also give satisfactory results. Confirmation of the diagnosis requires culturing of the pathogen, preferably on a blood-enriched medium. Gliding bacterial disease/tail rot disease (Flexibacter sp.): Control is mainly by chemotherapy. Antibiotic treatment Tail rot disease caused by gliding bacteria of the genus with erythromycin and spiramycin has proved effective. Flexibacter, is one of the diseases commonly found in Asian seabass in cages. The bacteria first gain entry Mycobacteriosis through damaged caudal fin, where the tissues are The etiological agents of mycobacteriosis, Mycobacterium gradually eroded away by the bacteria. The bacteria then marinum cause systemic, chronic infections in fish. The invade the muscular region, the muscles disintegrate and disease follows a chronic course and remains typical tail rot occurs. No pathological changes are asymptomatic for a long time. Superficial ulcers and normally observed in the internal organs. The disease exophthalmia are often the only external signs. Spleen usually affects seabass fry, 2 -3 weeks after their and kidney however are severely affected and are enlarged introduction sea cages. with granulomatous lesions that appear macroscopically 90 Central Marine Fisheries Research Institute From 14 - 23 December 2009 as whitish nodules. In advanced cases these lesions spread age, host specificity, immunity and the influences of host to liver, heart, mesentery etc. condition also play an important part in the host reaction to invasion by protozoa. Nocardiosis Nocardiosis is a chronic bacterial disease that affects both freshwater and marine fish. Many clinical characteristics of nocardiosis are similar to mycobacteriosis. Early signs of infection include anorexia, inactivity, skin discolouration and emaciation. In the late stages, nodular skin lesions may ulcerate or extend to skeletal muscle and visceral organs, causing abdominal distension. There is no effective therapy for this disease. The route of infection in fish is not known, but is probably through direct contact or contaminated food. Clean environment is an important factor in preventing the occurrence of the disease. Protozoans cause harm to fish mainly by mechanical damage, secretion of toxic substance, occlusion of the blood vessels, depriving the host of nutrition and rendering the host more susceptible to secondary infections. Some of the most common clinical signs are changes in swimming habits such as loss of equilibrium, flushing or scraping, loss of appetite, abnormal colouration, tissue erosion, excess mucus production, haemorrhages and swollen body or distended eyes. Cryptocaryon sp. Cryptocaryon sp. is the marine counterpart of the In addition to these more established pathogens, freshwater Ichthyophthirius species and similarly cause upcoming bacterial diseases potentially harmful for the white spot diseases in marine fish. Its morphology aquaculture species are being identified. A previously and life cycle is quite similar to that of the “Ich”. The unrecognized disease namely “pot belly or big belly” surface of invaded fish reveals white pustules or numerous disease caused by a facultative intracellular Gram- minute, greyish vesicles which are nests of cilliates negative bacterium has been identified. Infections with burrowing under the epidermis. They feed on the host’s this previously uncharacterized pathogen causes severe cells underneath the epithelium and cause heavy irritation visceral granulomatous lesions in Asian sea bass fry < 5 g resulting in excessive production of mucus and finally with an associated mortality rates of 70-80%. completely destroying the fine respiratory platelets of the gill filaments. On the skin, this parasitic protozoan causes Parasitic diseases Parasitic protozoa considerable lesions resulting in destruction of large areas of the epidermis. Secondary infection may complicate the situation and the host dies. The incidence of Cryptocaryon Protozoans are probably the most important group of sp. in seabass showed a distinct peak during low water animal parasites affecting fish. Many reports from all over temperature period. the world indicate great losses in cage culture caused by protozoans. Environmental factors affect the susceptibility of fish to certain protozoa. Oxygen concentration and temperature are the factors affecting both hosts and parasites. Since many protozoans transfer from fish to fish through the water, fish population density The presence of C. irritans in cage-cultured fish means that the cages are kept in too shallow waters. If logistically feasible, the cages should be moved in to an area where sufficient depth and currents prevent the theronts (free swimming infective stages) from re-infecting the fish. is an important factor. Tremendous infestation of Other important protozoan parazines affecting marine fish protozoans can occur in a relatively short time where fish cultured in cages are Trichodina sp., Brooklynella sp., populations are dense. Other factors such as host size, Henneguya sp. etc. 91 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Parasitic helminthes Worm diseases with the possible exception of those produced by monogenetic trematodes have not yet appeared to be a serious problem in seabass culture. This Parasitic crustaceans are generally introduced along with fish caught in the wild for culture, but several of them are transmitted by wild fish around the cages. Prevention is therefore difficult. is probably due in large part to their complex life cycle In addition to the infectious causes, diseases and and the difficulty in completing such cycles in the culture abnormalities due to environmental contaminants and system. Helminthes parasites which have been found in nutritional deficiencies have been recognized as important seabass include monogenetic trematodes, digenetic problems in fish culture whenever diets as well as control trematodes, nematodes and acanthocephala. or water quality become inadequate. Malnourishment or undernourishment of seabass under culture can result in Crustacean parasites slow growth, susceptibility to diseases or death. Crustaceans belonging to the Branchiura, Copepoda, In Asia, trash fish are widely used as feed in cage farming Isopoda and Amphipoda are frequently found on the body of marine finfish. Fry are often wild caught or derived from surface and/or gills of caged marine fish. wild-caught broodstock. Furthermore, legislation for and Parasitic copepods implementation of farming licenses and zoning policies are not in place in most Asian countries. Coupled with a The parasitic copepods are among the most devastating ‘gold rush’ mentality, this often results in too many fish of fish parasites. The mature female usually attaches to and too many farms in a concentrated area, which in turn the fish and feeds on the host. After copulation the female promotes disease transmission. The combination of all matures and produces egg sacs while the male dies. these factors, together with the diversity of organisms in The only branchiuran reported is Argulus sp. Most of the tropical waters, leads to a truly challenging disease copepods reported are caligids, which could cause epizootics situation. in the farms. Caligus sp. has caused big problems in cultured Furthermore, irresponsible use of antibiotics and seabass. They attach to the gills, buccal and opercular chemicals for disease control in aquaculture can lead to cavities, occasionally on the skin and fins of the seabass. residue problems, an increasing consumer concern, and Heavy infections can cause mass mortalities especially in to the development of drug resistance among the bacterial young fish. Lernanthropus sp. are found attached to the gill pathogens. In addition to developing antibiotic resistance, of seabass especially in cage cultured fish. Large numbers sick fish often do not eat and the efficiency of delivering of this parasite can cause anaemia to the fish host. antibiotics orally is often questionable. The use of Parasitic isopods antibiotics is a curative measure to treat an existing infection; in contrast, vaccination is a preventative Isopods which closely resemble Aega sp. have been found measure, dependent on the immune system of the animal. abundant in cage-cultured seabass. The parasite always Vaccines can act against bacterial, viral and, at least attaches to the gills of its host. Clinical signs of infected experimentally, parasitic infections and they will usually seabass are as follows: fish lose appetite, become anemic act only against the targeted pathogens. In Asia, with and grow very slowly. Quick death can occur in 2–3 days the exception of Japan, few fish vaccines are yet in heavily infected young fish. Nerocila sp. and Gnathia commercially available. The major advantages of sp. have also been reported in seabass. prophylactic vaccination over therapeutic treatment are 92 Central Marine Fisheries Research Institute From 14 - 23 December 2009 that vaccines provide long-lasting protection and leave diseases has become more and more important in the no problematic residues in the product or environment. cultivation of aquatic animals. Good health management Asian aquaculture will continue to grow at a fast pace is the best way for disease control. Collectively, this due to both area expansion and production intensification. includes the use of healthy fry, quarantine measures, Under these conditions, the prevalence and spread of optimized feeding, good husbandry techniques, disease infectious diseases will unavoidably increase as a result monitoring (surveillance and reporting), and sanitation as of higher infection pressure, deterioration of well as vaccination, and biosecurity measures when environmental conditions and movement of aquatic diseases do occur. Overall, the emphasis must be on animals. Accordingly, the effective control of infectious prevention rather than treatment. 93 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Open sea cage culture in IndiaA sociological perspective Ramachandran, C. Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India ramchandrancnair@gmail.com Introduction Marine cage culture is the latest innovation in Indian mariculture scenario. The first cage was demonstrated in Visakhapatanam in 2007-08. The logic of the floating cage culture technology is the conversion of marine space into a controlled production system. This entails a number of socio-political issues apart from the technological ones. mature industry in these countries (Grottum and Beveridge 2007). In the Asian region, China has attained significant strides in off shore cage culture. Within the span of a decade (1990-2000) and with an investment of more than US$10 million, China has deployed about 4000 such cages yielding about 2 lakh tons ( Chen and Chen 2008). Prominent among them is the changing context of marine India’s entry into the arena of off shore cage culture is tenure in the country. This paper analyses such issues very recent and this marks a significant milestone in the based on a preliminary study conducted in some of the mariculture pursuits of the country. The history of locations where the cage demonstration has been mariculture research in India dates back to early seventies implemented. The major sociological framework employed when pioneering attempts were made by CMFRI to farm in the analysis is that of the Actor –Network Theory (ANT) mussels in the inshore waters using lines. Though the proposed by Latour (2007). Thus the methodological technology was successfully demonstrated, it did not objective was to explore the actor- networks at different capture the imagination of the fisher folk for reasons locations using participatory protocols. obvious. The major stumbling block was the absence of a “culture mindset” which was partly due to resource The idea of cultivating fish in the open sea through abundance amenable to exploitation through capture cages is of recent origin. Open sea cage culture is being fisheries. With the capture fisheries production leveling posed as an answer to increasing demand for food in off in the recent years the potential for the open sea cage the context of the declining yield trend shown by culture is huge. capture fisheries (especially when the Chinese catch Visakhapatanam has come as a shot in the arm to our excluded) and the problems faced by the land based – mariculture aspirations. aqua farming technology. The pioneers in this technology are countries like Norway, Japan and USA. The success demonstrated at Objective and methodology After about three decades of intense research and It is in this context that the present study was undertaken development activities cage culture has become a to assess the perception of the stakeholder constituency 94 Central Marine Fisheries Research Institute From 14 - 23 December 2009 and to reflect on the challenges and prospects of open mainly determined by innovation characteristics (as sea mariculture. The cage culture is a newly introduced defined by Rogers, 2003) only can be assessed now. innovation and could be either adopted or rejected by the stakeholders. An individual’s decision to adopt or reject a new practice passes through several stages, and does not happen at once. Innovation diffusion studies have recognized the adoption/non-adoption of a new introduced practice is influenced by whether or not it matches with the adopters’ needs, situation, and perceptions of the innovation (Rogers, 2003).The rate of adoption might differ among individuals depending on his/ The location of the sites where the preliminary study was conducted is depicted in Table1. It also shows the current status of the culture in these sites. As it can be seen some of the sites one demonstration was over and in other places the first series of demonstration was in different stages of operation. There was continuous access to all the operations at Munambam which was covered during (9/12/08 to 18/04/09). her level of innovativeness. The more innovative an A notable feature of the innovation transfer model being individual the shorter is the adoption time. Since the attempted across the sites is the way in which the various innovation is in the nascent stage of adoption it is not agencies and institutions are integrated. The dominant possible to draw of picture of its diffusion. The perception mode is that of Public-Private Partnership. The table below of people on the probability of its adoption, which is gives an over all view on this aspect. Table 1 Sites of open sea cage culture visited Site State,district Distance from cmfri centre Status of cage remarks 1. ChaumukhBaliapal Orissa, Baleswar/ Balasore From Viskah, about 700km Cage installed in the sea, Very good cooperation from 4000 fingerlings of sea the fisheries department and bass stocked the fisher folk 2.Visakhapatanam AP, Visakah About 5km Second cage P monodon stocked 3.Iskapalli AP, Nellore About 200 km from Chennai -Two cages installedModifications done to stock P. monodon and lobsters Fisher folk evince keen interest 4.Pulikat Tamil Nadu, About 50 km from Chennai Ready for stocking lobsters Good support from the NGO and fisher folk. Fishers more interested as this is the second time 5.Munambam Kerala About 30 km from Kochi Harvest done Pre mature harvest due to drifting of cages; growth parameters promising 6.Vizhinjam Kerala About 18 km from Thiruvananthapuram Table 2 The fishermen group has gained more confidence Harvest done Modes of institutional arrangements Site Mode ChaumukhBaliapal(orissa) PPP Society of the traditional fisherfolk+State Department of Fisheries+CMFRI+NFDB Details Visakhapatanam (AP) do Fishermen society +lead role by a fisherman leader+DF+CMFRI+NFDB Iskapalli,Nellore(AP) do Fishermen society +lead role by a fisherman leader + DF+ CMFRI+ NFDB Pulikat, Chennai ( TN) do Fishermen society +NGO +DF+CMFRI+NFDB Munambam Fishermen group +CMFRI+NFDB Vizhinjam do 95 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi fund of the Government. In Balasore, the group was willing Perception of stakeholders Perceived attributes of an innovation such as relative advantage, complexity, compatibility, trialability, and to put operational expenditure provided the cage was given to them. perceived risks have been used extensively in previous It is to be noted that the demonstration is just in progress innovation studies to evaluate innovation adoption. in Balasore. Nevertheless the stakeholders here have a (Rogers 1983) defines relative advantage as ‘the degree much more favorable perception towards the innovation. to which an innovation is perceived as being better than This could be because of certain socioeconomic the idea it supersedes’. Complexity is defined as ‘the peculiarities of the village like backwardness, homogeneity degree to which an innovation is perceived as relatively of the group, and the presence of a culture mindset owing difficult to understand and use’]. Trialability is defined as to the fact that almost all the fishermen families possess ‘the degree to which an innovation may be experimented farm lands for cultivation. The fishermen in the west coast with, on a limited basis’ Compatibility is defined as ‘the ( represented by two sites) was found to be a bit reserved degree to which an innovation is perceived as consistent as only medium response was obtained on this count. This with the existing values, past experiences, and needs of must be read in tandem with their perception on innovation potential adopter’. Perceived risk is defined as the degree characteristics which was found to be low on to which an innovation is perceived to be economically risky. Another remarkable observation is the increase in level of confidence shown by the fisherfolk after the The stakeholders in general showed enthusiasm towards the innovation in all the locations. Though this is encouraging it needs to be qualified with the facts that the demonstrations are being carried with financial support to the stakeholders. But the real litmus test is their willingness to adopt the innovation entirely on their own. When this question was asked on a Likert type scale the responses obtained were revealing. The * sign indicates the perception before the demonstration and $ indicates the same after the demonstration. Visakahpatanam was found to be more positive on this count. demonstration of the technology in one season. When the perceived innovation characteristics were considered the pattern obtained has been deputed below. The response was not collected from the two places where the demonstration was not completed. The innovation characteristics registered a better perception in Visakhapatanam. This could be due to many facts like a) the positive impact due to the success of the first demonstration b) the role played by Mr Polanna who happen to be the leader of a state level fishermen association Table 3 Perceived adoptability across locations 1(Blsr) High Medium 2(vsk) 3(nlr) 4(plkt) 5(mnmbm) 6(vzj) $ $ $ * * * * $ * * Low (High-above 75% of response, Medium-50-75% Low –below 50%) Though high initial cost is a perceived deterrent across the locations, the Visakhapatanam group was optimistic to get financial assistance through the Tsunami assistance c) better accessibility to technical advise and supervision from CMFRI d) higher innovativeness of the group 96 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Table 4 Perceived innovation characteristics Innovation characteristic 1(Blsr) 2(Vsk) 3(Nlr) 4(Plkt) 5(Mbm) 6(Vzj) Relative advantage ( high) $$$ $ $ $ Complexity ( low) $$ $ $ $ Trialability ( high) $$$ $$ $ $ Compatibility ( high) $$$ $$ $ $ Perceived risk( low) $$ $ $ $ ($$$-above 75% Agree, $$-50-75% Agree,$-less than 50% agree) Prospects and Challenges Though it is too early to comment on the future of the innovation in the Indian scenario some reflections made in this direction seems not to be out of place. The question is will the technology get adopted and diffused? The answer depends on three major factors a) technological b) socio-economical and c) political/governance. Since the technological factors are being addressed by the concerned persons I limit my discussion to the sociological and political aspects here. Sociological factors The major factor that influences the innovation decision process is the extent to which the candidate innovation meter. Another factor is the price they get for the cagecultured fish. Though high value fishes are being recommended now, their price is dependent on the market vulnerability. Another factor is the delay in the financial reward. Unlike capture they have to wait for about five to six months for the harvest. But compared to the former, cage culture is less risk prone. But fishermen were of the opinion that if the season of the culture is planned in such a way that the harvest synchronizes with the lean season/high demand season like festivals they could earn better price. Since cage culture offers control over the production system possibilities of getting premium price by way of organic certification or other certifications could be explored. meets the felt needs of the incumbent adopter. The Though threats like poaching or community-agreed relative advantage of this innovation has been favouarbly vandalism are real they can be remedied if the community perceived. The fisher folk in general feel that the capture is vested with the ownership of the cages. Innovativeness fisheries sustainability is in peril and they are in the look of the fisherfolk need to be tapped to the maximum extent out for alternative livelihood sources. It can be assumed possible in all the aspects like selection of sites, species, that the cage culture in this aspect has captured their feed, cost cutting strategies etc. imagination if one goes by the enthusiasm shown by the people. The emergence of a culture mindset is a welcome sign because fishermen are believed to be still in the hunter- gather mindset. Political/governance factors The cage culture being a point of departure against the conventional sense of marine tenure it poses many There are push and pull factors behind the adoption of challenges in this regard. To established ocean users cage any innovation. One of the major deterrents is the culture is a new system of property that regulates access perceived high initial cost. But if the cages are made and usage of marine resources. Until recently the ocean available to the fishermen group at a subsidized cost it is was considered to be the last of the commons, where well likely to be adopted. Attention needs to be given to ownership is based on the labour that fishermen invested cost cutting strategies in the cage fabrication. The cost in the act of catching them. The marine tenure system of HDPE cages in China is said to be only Rs600/cubic prevalent in the country, though its enforcement is feeble, 97 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi grant rights to fishing territories they do not guarantee surmount. No social scientist who has ever experienced that fish would not migrate out of these territories. Until the frustrating pangs of establishing a “connection “ with a fish is caught nobody is considered to be a legitimate the fisherfolk can fail to see the transformation of cages, owner of that fish. The concept of cage culture thus marks with its positive image of being a tangible production a significant departure from this notion. So the need of system innovation, as becoming emotional bridges. the hour is to chalk out a suitable marine property rights policy giving due weightage to the rights of the community Concluding remarks but not forestalling socially committed corporate bodies It is too early to predict the future of the cage culture in in entering the scenario on a Public Private Partnership India. The innovation has many challenges as well as mode. A system of Public hearing as has been practiced opportunities. To tackle the challenges a great deal of in Hawai ( Suryanata and Umento 2002) could be followed discussion, planning and coordination is required to create in legitimizing commercialization of marine space. dynamic networks on a value chain basis. However its fate lies in the collective will, social capital and Cage as a new metaphor institutional capacity of a number of agencies and There is nothing more puzzling than a proposition that institutions involved. The lessons from the countries who views Open Sea Cages as bridges! But this is the are ahead of us could be of much use in terms of not only concluding remark I would like to pose. Yes, the cages the technology but also the marine farming governance. have started acting as socio-psychological bridges The demonstrations being undertaken in different parts between the marine fisheries R&D and the fisherfolk along of the country needs to be viewed in the perspective of the coast of this country. The Indian coastal villages never Multi Locational Trials and there is an urgent need to had such a “bridge’ built through their collective psyche, convert such collective knowledge into location specific except perhaps the few mariculture interventions done policies, norms, networks and practices. in the late seventies. There always has been an intangible barrier between the fishermen and the kind of scientific knowledge, (especially the stock assessment knowledge which is the main mandate of CMFRI) that has been generated by the researchers. Being relevant only at a wider policy level, there is no wonder that, this knowledge base could hardy capture the imagination of the fisherfolk. They often found the research system as an anathema, informing governments to make policies that went against their immediate interests (like mesh size regulations/ reduction in fishing effort/even the seasonal fishing bans). The scientific advice was deemed to be with a touch of inherent negativity. This has led to the development of an annoying sense of mistrust among the fisherfolk and this has been the biggest communication barrier an extension scientist working in the marine sector has to References Chen J , Xu, H. and Chen Y., 2008. Marine fish cage culture in China. In A. Lovatelli, M.J. Phillips, J.R. Arthur and K. Yamamoto. (eds). FAO/NACA Regional Workshop ftp://ftp.fao.org/docrep/fao/011/i0202e/i0202e14. Grottum J. A. and Beveridge,M., 2007. A review of cage aquaculture .Northern Europe. In M Halwart,D ,Soto and JR Arthur (eds).Cage Aquaculture-regional reviews and global overview. FAO Fisheries Technical paper no 498:126-154. Latour, Bruno, 2007. Reassembling the social-An introduction to Actor- network theory. Oxford University Press.pp301. Rogers, E. M., 1983.Diffusion of innovations. Free Press , New Ypork.pp550 Suryanata, K. and Umemeotot,K., 2002. Capturing fugitive resources in a globalised economy: the case of marine aquaculture in Hawai.dlc.dlib.indiana.edu/archive. 98 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Grow out culture of seabass in cages Boby Ignatius Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India bobycmfri@yahoo.co.in Aquaculture of Lates calcarifer, known as seabass, was small coastal cage farms. Often these farms will culture commenced in the 1970s in Thailand, and rapidly spread a mixture of species, including Seabass, groupers (Family throughout Southeast Asia. In India also it is a sought Serranidae, Subfamily Epinephelinae) and snappers (Family after fish in many states. The grow-out phase involves Lutjanidae). Australia is experiencing the development of the rearing of the seabass from juvenile to marketable large-scale Seabass farms that reflect the industrialized size. Marketable size requirement of seabass vary country style of aquaculture seen in Europe, where Seabass to country e.g. in Malaysia, Thailand, Hong Kong and farming is undertaken outside the tropics, recirculation Singapore, the normally accepted marketable size of production systems are often used (e.g. in southern seabass is between 700–1200 g while in the Philippines, Australia and in the north-eastern United States of marketable size is between 300–400 g. The culture period America). in grow-out phase also vary from 3–4 months (to produce 300–400) to 8–12 months. The success of marine cage culture of seabass and its economical viability have contributed significantly to large scale development of this aquaculture system Most seabass grow out is undertaken in net cages. The cages are either floating or fixed and range in size from 3 x 3 m up to 10 x 10 m and 2 -3 m deep. The mesh sizes of these cages ranges from 2-8 cm. Seabass are reared from juvenile to marketable size varies depending on water Among the attributes that make Seabass an ideal quality and the environmental conditions of the culture candidate for aquaculture are: site. Floating cages can be stocked more than stationary z z It is a relatively hardy species that tolerates crowding cages. This is because floating cages are usually set in and has wide physiological tolerances. sites with better aquatic environmental conditions such The high fecundity of female fish provides plenty of material for hatchery production of seed. as deeper water, smaller fluctuation of water salinity, more rapid circulation and further away from sources of pollution. z Hatchery production of seed is relatively simple. z Seabass feed well on pelleted diets, and juveniles are Suitable site for seabass cage culture easy to wean to pellets. Criteria for selecting a suitable site for cage culture of Seabass grow rapidly, reaching a harvestable size (350 seabass include: z g – 3 kg) in six months to two years. a. Protection from strong wind and waves. The cage Today Seabass is farmed throughout most of its range, culture site should preferably be located in protected with most production in Southeast Asia, generally from bays, lagoons, sheltered coves or inland sea. 99 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi b. Water circulation. The site should preferably be located Stocking density in cages is usually between 40–50 fish in an area where influence of tidal fluctuation is not per cubic meter. Two to three months thereafter, when pronounced. Avoid installing cages where the current the fish have attained a weight between 150–200 g, the velocity is strong. stocking density should be reduced to 10–20 fish per c. Salinity. Suitable site for seabass culture should have a salinity ranging from 13–30 ppt. d. Biofouling. The site should be far from the area where biofoulers abound. cubic meter. Generally, increase in densities results in decreased growth rates. Higher stocking densities require more monitoring of water quality and fish health, additional aeration and higher water exchange rates. e. Water quality. The site should be far from the sources There should be spare cages as these are necessary for of domestic, industrial and agricultural pollution and transfer of stock and to effect immediate change of net other environmental hazards. in the previously stocked cage once it has become clogged The optimum temperature for Seabass culture is 28°C, with acceptable growth rates between 26-30°C. Temperatures below this range will result in decreased metabolism and growth. Seabass generally stop feeding at temperatures below 20°C. At optimum temperatures, with fouling organisms. Changing cages allows for grading and controlling stock density. The choice of netting mesh size of fish Mesh size Size of fish 0.5 cm 1–2 cm 1 cm 5–10 cm 12 months. 2 cm 20–30 cm The water quality parameters which are considered of 4 cm bigger than 25 cm Seabass can be raised to market size (500g) between 6- minimum range for cage culture of seabass The suitable water quality for cage culture of seabass. Parameters Ranges Feeds and feeding Due to the carnivorous nature of Seabass, a high protein diet is required for efficient growth. Commercial diets are pH 7.5–8.3 Dissolved Oxygen 4.0 – 8.0 mg/L. Water salinity 10 – 31 ppt. Water temperature 26 – 32 °c Ammonia — nitrogen less than 0.02 mg/L. of 1.5-2:1 (kg of food: kg of weight growth), however lower Hydrogen sulfide none FCRs have been reported by some industry members. readily available from a number of feed manufacturers and are generally produced in a floating or sinking pellet. Food conversion ratios (FCRs) for Seabass should be in the range The stocking densities used for cage culture generally Trash fish is the main feed for seabass culture. Trash fish range from 15 to 40 kg/m³, although densities may be as should be fresh and clean. Trash fish used in Thailand are high as 60 kg/m³. Prior to stocking seabass juvenile in sardines and other small marine fish. The trash fish should cages, fish should be acclimatized to the ambient be chopped and fed twice a day, in the morning and temperature and salinity prevailing in the cages. The fish afternoon. The size must be suitable for the size of the should be graded into several size groups and stocked in mouth of the fish. The farmers should give the feed slowly separate cages. The stocking time should be done in the and watch the fish. Feeding should be stopped when the early mornings (0600–0800 hours) or late in the evening fish no longer come up to the surface; it shows that the (2000–2200 hours) when the temperature is cooler. amount of feed is enough for them. 100 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Feed is the major constraint confronting the seabass culture industry. At present, trash fish is the only known feed stuff used in seabass culture. Chopped trash fish are Monthly growth (g) of seabass at different stocking densities in cages ( Sakaras, 1982) Culture Period 16/m Stocking density 24/m 32/m given twice daily in the morning at 0800 hours and 0 afternoon at 1700 hours at the overall rate of 10% of total 1 biomass in the first two months of culture. After two 2 months, feeding is reduced to once daily and given in the 3 262.9 afternoon at the rate of 5% of the total biomass. Food 4 326.2 332.0 311.5 5 381.1 384.9 358.8 6 498.6 487.1 455.4 should be given only when the fish swim near the surface to eat. Vitamin premix may be added to the trash fish at 67.8 67.8 67.8 132.3 137.5 139.2 225.2 229.1 225.5 267.5 264.1 a rate of 2 percent, or rice bran or broken rice may be Main problem in grow out culture are feeding and added to increase the bulk of the feed at minimal cost. prevention of cannibalism in young fishes. In order to Food conversion ratios (FCRs) for Seabass fed on trash reduce losses due to cannibalism, grow out is performed fish are high, generally ranging from 4:1 to 8:1. in two phases, viz. nursery phase up to a size of 20g in Growth nursery ponds/cages and grow out phase The size of the feed must be suitable for the size of the mouth of the Growth is highly variable and depends on various factors fish. The farmers should feed fish slowly and watch them. including temperature, feeding rate, feed quality and Feeding should be stopped when the fish no longer come stocking density. Generally fish grows from fingerling to up to the surface which indicates that the amount of feed 300-500g in 6-12 months and to 3kg in 2 years. is enough for them. Food conversion rates of seabass also Stocking larger size seed fish attains greater individual depend on the quality and quantity of trash fish. Normally, and total weight per cage than smaller ones. Seabass size seabass can grow at an average of I kg/yr. Survival rates ranges from 10-17cm in length are suitable for culturing for marketable fish culture are about 80-95 percent in in cages with grow out at 6- 7 months. normal culture conditions. 101 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Open sea Cage culture: carrying capacity and stocking in the grow out system Shoji Joseph Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India sjben@yahoo.com Developing open sea cage farming is a new way of the environment can sustain indefinitely, given the food, providing employment to fishermen transferring from fish habitat, water and other necessities available in the capture to aquaculture. It will also create significant socio- environment. In ecological terms, the carrying capacity economic influences in the future. The near target of cage of an ecosystem is the size of the population that can be culture is that marine fish farming will become a main supported indefinitely upon the available resources and force in aquaculture sector. The open sea cage culture services of that ecosystem. Living within the limits of an has been expanding in recent years on a global basis and ecosystem depends on three factors: it is viewed by many stakeholders in the industry as the z the amount of resources available in the ecosystem aquaculture system of the millennium. The Asian seabass, z the size of the population, and Lates calcarifer, known as “Kaalangi” in Kerala is an z the amount of resources each individual is consuming. important candidate finfish species for sea cage farming. Carrying capacity A major consideration in the site selection process should be the carrying capacity of the site which indicates the maximum level of production that a site might be expected to sustain. Intensive cage fish farming results in the production of wastes which can stimulate productivity and alter the abiotic and biotic caracteristics of the water body, whilst less intensive methods can result in over croppping of algae and a fall in productivity. Hence profitability or even viability may be seriously affected. Therfore it is extremely important for all concerned with cage fish farming to have an accurate evaluation of the sustainbale levels of production at a particular site before culture. A simple example of carrying capacity is the number of people who could survive in a lifeboat after a shipwreck. Their survival depends on how much food and water they have, how much each person eats and drinks each day, and how many days they are afloat. If the lifeboat made it to an island, how long the people survived would depend upon the food and water supply on the island and how wisely they used it. A small desert island will support far fewer people than a large continent with abundant water and good soil for growing crops. In this example, food and water are the natural capital of the island. Living within the carrying capacity means using those supplies no faster than they are replenished by the island’s environment: using the ‘interest’ income of the natural capital. A community that is living off the interest of its The carrying capacity of a biological species in an community capital is living within the carrying capacity. environment is the population size of the species that A community that is degrading or destroying the 102 Central Marine Fisheries Research Institute From 14 - 23 December 2009 ecosystem on which it depends is using up its community Feed losses are inevitable during fish culture for a number capital and is living unsustainably. So, in the context of of reasons; but the left over food that is not be eaten is sustainability, carrying capacity is the size of the actually not a loss in the culture systems; instead population that can be supported indefinitely upon the contribute to the wastes from the operation. available resources and services of supporting natural, Manufacturers estimate that 2% of feed is ‘dust’, due social, human, and built capital. largely to the crumbling of pellets during packing and Within the context of aquaculture, environmental carrying capacity is defined as the maximum number of animals transport and thus at least 2% of commercial feeds will be uneaten and contributes to the water body. or biomass that can be supported by a given ecosystem In order to determine the potential of a water body for for a given time. This is particularly important to intensive enclosure, the productivity of the same prior to aquaculturists who seek to optimize the economic value exploitation must be assessed through measurement of or yield per unit area, or regulatory authorities who are the steady-state total-P concentration, The development interested in minimizing the negative impacts aquaculture capacity of a lake or reservoir for intensive cage and pen can have on the natural environment through the issuing culture is the difference between the productivity of the of permits or granting concessions. water body prior to exploitation, and the final desired level Estimation of Carrying capacity of productivity. As stated above, [P] can be used as a productivity indicator. However, it must be decided In semi-intensive and intensive systems the number of whether it is then mean annual algal biomass, or the peak fish that may be stocked will be limited by the “carrying annual algal biomass, as measured by chlorophyll levels capacity” of the water. This can be calculated using [ch1] and [ch1]max respectively, that we wish to predict. standard methodology. Before considering how to model Since fish are usually held in cages throughout the year, the impact of cage fish culture on the environment, the it is the latter parameter which should be considered. rationale behind using this method to increase fish production should be understood. The modeling is based The capacity of a water body for intensive cage and pen on the assumptions that algal population densities are fish culture is the difference, Ä [P], between [P] prior to negatively correlated with water quality in general and exploitation, [P]i, and the desired/acceptable [P] once fish growth and survival of fish stocks in particular, and that culture is established, [P]f. phosphorus (P) is the limiting nutrient which controls phytoplankton abundance in the water bodies. I.e. Ä [P] = [P]f - [P]i Phosphorus and, occasionally, light are the principal Ä[P] is related to P loadings from fish enclosures, Lfish, the factors limiting production, and thus the net addition or size of the lake, A, its flushing rate, ñ, and the ability of uptake of P or materials which greatly influence the light the water body to handle the loadings (i.e. the fraction of climate will alter productivity. Phosphorus is an essential Lfish retained by the sediments, Rfish):- element required by all fish for normal growth and bone development, maintenance of acid-base regulation, and lipid and carbohydrate metabolism. Diets deficient in P can suppress appetite, normal food conversion and growth, and under extreme circumstances affect bone formation and lead to death. 103 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi The acceptable/desirable change in [P], Ä [P] (mg m-3), is Here nitrogen and phosphorus are the water quality determined as described above, and z can be calculated parameters considered for the calculation of carrying from hydrographic data obtained either from literature or capacity. The simulated results showed the maximum survey work:- nitrogen and phosphorus concentrations were 0.216 mg/ Where V = volume of water body (m3) and A = surface area (m2) the flushing rate, (y-1) is equal to Qo/V, where Qo is the average total volume out flowing each year. Qo can be calculated by direct measurement of outflows, or in some circumstances can be determined from published data on total long-term average inflows from catchment area surface runoff (Ad.r), precipitation (Pr) and evaporation (Ev), such that Qo = Ad.r + A(Pr - Ev) (see Dillon and Rigler, 1975, for further details). L and 0.039 mg/L, respectively. In most of the sea area, the nutrient concentrations were higher than the water quality standards. The calculated environmental carrying capacity of nitrogen and phosphorus in Xiangshan Harbor were 1,107.37 t/yr and 134.35 t/yr, respectively. The results showed that the waste generated from cage culturing in 2000 has already exceeded the environmental carrying capacity. Unconsumed feed has been identified as the most important origin of all pollutants in cage culturing systems. It suggests the importance of increasing the feed The retention coefficient, R, can be determined utilization and improving the feed composition on the experimentally by measuring the mean annual inflow and basis of nutrient requirement. For the sustainable outflow [P], [P]i; and [P]o respectively:- development of the aquaculture industry, it is an effective management measure to keep the stocking density and pollution loadings below the environmental carrying Marine cage aquaculture produces a large amount of waste that is released directly into the environment. To effectively manage the mariculture environment, it is important to determine the carrying capacity of an aquaculture area. In many Asian countries trash fish is dominantly used in marine cage aquaculture, which contains more water than pellet feed. The traditional nutrient loading analysis is for pellet feed not for trash fish feed. So, a more critical analysis is necessary in trash fish feed culturing areas. Based on the hydrodynamic model and the mass transport model in Xiangshan Harbor, the relationship between the water quality and the waste discharged from cage aquaculture has been determined. Here corresponding to FCR (feed conversion ratio), dry feed conversion ratio (DFCR) was used to analyze the nutrient loadings from capacity. The DFCR-based nutrient loadings analysis indicates, in trash fish feed culturing areas, that it is more critical and has been proved to be a valuable loading calculation method. The modeling approach for Xiangshan Harbor presented here is a cost-effective method for assessing the environmental impact and determining the capacity. Carrying capacity information can give scientific suggestions for the sustainable management of aquaculture environments. It has been proved that numerical models were convenient tools to predict the environmental carrying capacity. The development of models coupled with dynamic and aquaculture ecology is a requirement of further research. Such models can also be useful in monitoring the ecological impacts caused by mariculture activities. marine cage aquaculture where trash fish is used. The Fish stocking in the cages environmental carrying capacity of the aquaculture sea The minimum recommended stocking density for common area can be calculated by applying the models noted above. carp, tilapia, and catfish is 80 fish/m3. A recommended 104 Central Marine Fisheries Research Institute From 14 - 23 December 2009 maximum stock density for beginning farmers is the cage(s) to assure that the weight does not reach the number of fish that will collectively weigh 150 kg/m3 carrying capacity of the water body during culture. when the fish reach a predetermined harvest size (Schmittou, 1991). The smallest recommended fingerling Maximum volume of cages (m3) = 2.6a* Where: a = total surface area of water body (1,000s of m2) size for stocking is 15 g. A 15-g fish will be retained by a 13-mm bar mesh net. Larger fish can also be stocked into * The constant 2.6 is derived below cages. Survival rates in well-placed and well-managed 400 kg cages are typically 98 to 100 %. Unless greater mortality 1,000 m2 pond is expected, no adjustment is needed to calculate stocking 150 kg density. An example of how to calculate the number of fish to stock per cage follows: Assume that a farmer wants harvest fish weighing 500 g from a 1m3 cage. m3 cage Grow out of the sea bass culture starts as it transfers to Total fish weight at harves t= 150 kg/m 3 the cages from the nurseries. Juveniles of sea bass reared Number to stock = 300 fish (300 x0.5kg) in the nurseries of size 10 - 15 cm in length (25 – 50 g in Desired average fish weight = 0.5 kg at harvest Production = 150 kg/m3 wt) can be transferred to the cage for the grow-out. The For a harvest of fish averaging 200 g, the number of fish to stock would be: Number to stock = 750 fish/m 0.2 kg x 750 = 300 kg/m 3 3 The carrying capacity of a body of water limits the weight of fish that can be cultured. Stocking so many fish that the carrying capacity is exceeded will result in increased stress, disease, and mortality, and reduced feed stocking density in the cages varies from 20 – 25 kg/m3 in the final harvest time. So with a final weight of expectation of 1 kg fishes in harvest time after a period of 6 – 8 months; from the cages the stocking density varies from 25 – 30 fishes / m3 for the sea bass. Care must be taken to avoid handling stress and other physiological stresses as maximum as possible while transport and stocking. conversion efficiency, growth rate, and profit. Generally, Once when the carrying capacity is determined in a culture 1,000 m of water surface area is needed to support 400 system, and optimum stocking is done accordingly, open kg of fish. A calculation can be used to determine the sea cage culture can be a successful alternative for any maximum number of fish which can be stocked into a species of high value marine fish. 2 105 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Growth in fleet size and investment in marine fisheries and scope for open sea mariculture Sathiadhas, R. Central Marine Fisheries Research Institute, Post box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India rsdhas@rediffmail.com Fishing has been considered as a primary livelihood option sea mariculture by adopting location specific appropriate since time immemorial, for the occupants of the coastal technologies. belt in India, stretching along 8129 kms. Fisheries play a predominant strategic role in the economic activity of our country by its contribution to national income, food and employment. It supports the deprived coastal community and serves as an important foreign exchange earner contributing substantially to food and nutritional security. It is also a principal source of livelihood to people in coastal areas. Fisheries contribute about 1 per cent of India’s GDP, which forms about 4.12 per cent of the agricultural GDP (2003-04). The total fish production The backdrop of fisheries legislations enacted in India traces back to 1857, when the Indian Fisheries Act was endorsed. It was meant to regulate riverine fisheries and fisheries in inshore waters, to prohibit the use of poisons and dynamite in fishing, and to protect fish resources in selected waters through regulation of, among other things, the erection and use of fixed engines (the reference is to nets, cages, traps, etc.), the construction of weirs, the use of nets of certain types and dimensions, etc. during the four decades (1950-51 to 1990-91) showed an The present day scenario is governed by various sets of annual average compound growth rate that varied enactments essentially having bearing on the marine between 3.35 to 4.62 percent. About 12.2 lakh fisherfolk fisheries sector. These legislations include Maritime Zones operate diverse types of craft-gear combinations with Act (1976) which recognizes the sovereign rights to regional and seasonal variations all along the Indian conservation and management of living resources in the coastline. The secondary sector provides employment to Indian EEZ, in addition to their exploration and more than 15 lakh people and another one lakh people is exploitation. Another important regulation governing the employed in the tertiary sector. Decline in catch rates marine fisheries is Maritime Zones of India (Regulation of coupled with increasing domestic and international Fishing by Foreign Vessels) Act (1981) and Rules (1982). demand of high value species has resulted into more Fisheries within the 12-mile territorial limits are managed conflicts in sharing of resources, increase in migration of under the Marine Fishing Regulation Acts (MFRAS) of the fishing units and labourers, emergence of multiday fishing maritime States of India. The main emphasis of MFRAS is even extending beyond 15 days and consequent on regulating fishing vessels in the 12-nautical mile socioeconomic disturbances. In this context, there is good territorial sea, mainly to protect the interests of fishermen scope to increase our food fish production through open on board traditional fishing vessels. Thus, the Act has been 106 Central Marine Fisheries Research Institute From 14 - 23 December 2009 mainly used for the purpose of maintaining law and order legislation so far enacted by the central Government and at sea. The MFRAS were first implemented in the States various state Governments focussed mainly to regulate of Kerala and Goa in 1980. They were subsequently the harvesting of open sea resources rather than enacted in other States, the latest being in 2003, in considering the farming in the sea. Gujarat. While the earliest MFRAS were enacted only for At present (2003-04) there are 2251 traditional landing regulation of fishing vessels along the coastline of the centres, 33 minor and 6 major fishing harbours in the State, the Gujarat MFRA provides for protection, marine fisheries sector of India. About 1.77 lakh of fishing conservation and development of fisheries in inland and crafts are in operation comprising 76596 traditional non- territorial waters of the State of Gujarat and for regulation mechanised fishing crafts, 50922 motorized crafts and of fishing in the inland and territorial waters along the 49070 mechanized crafts operating different gears as coastline of the State. The Coastal Regulation Zone shown in Table 1. Protection Act, (1986) outlines a zoning scheme to Table 1 Growth rate of marine fishing fleets in India (1961-62 to 2003-04) Year 1961-62 1973-77 1980-81 1997-98 2003-04 SECTOR Non-mechanised Number Growth Rate (%) Motorised Number Growth Rate (%) Mechanised Number Growth Rate (%) Number 90424 106480 137000 160000 76596 — — — 32000 50922 — 8086 19013 47000 49070 90424 — 156013 239000 176588 — 18 29 17 -52 — — — — 59 — — 135 147 4 Total Growth Rate (%) — — 73 53 -26 regulate development in a defined coastal strip. The The trends in the growth rate of fishing units indicate the Notification defines the coastal stretches of seas, bays, possible phasing out of non-mechanised Canoes at least estuaries, creeks, rivers and backwaters which are in certain regions, which ultimately reflected a negative influenced by tidal action in the landward side, up to 500 growth of 52 per cent by them during 1997-98 to 2003- m from the high-tide line (HTL) and the land between the 04. This downtrend is compensated in the motorised low-tide line (LTL) and the HTL, as the CRZ. The sector implying large-scale motorisation of existing Environment Protection Act, (2002) authorizes the traditional crafts. Mechanised crafts displayed a major Central government to protect and improve boom during 1980s and 1990s. The growth rates were environmental quality, control and reduce pollution from 135 and 147 per cents respectively in 1980 and 1997, due all sources, and prohibit or restrict the setting and/or to diversification and extended area of operation. While operation of any industrial facility on environmental mechanized trawlers and gillnetters are common all over grounds. The Biological Diversity Act (2002) provides for Indian coast, dolnetters are popular in Gujarat and the conservation of biological diversity, the sustainable Maharashtra coasts, purseseines in Goa, and Karnataka use of its components and, significantly, the fair and coasts, pair trawling in Tamil Nadu and sona boats in equitable sharing of the benefits arising out of the use of Orissa coasts, depending on the regional and seasonal biological resources, knowledge and related matters. Open abundance of resources. When the technical efficiency sea mariculture requires adequate legislative support from of a particular gear is better than the other, the lesser the Government for leasing out of suitable sites. The efficient gears gradually disappear from the operation. 107 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi The gross capital investment on fishing units in Indian most of the non-mechanised fishermen are having one marine fisheries sector during 2003-04 works out at Rs. or two fishing nets, which are not sufficient for efficient 10,532crore in which mechanised sector constitutes about operation for the whole year. Rs. 9,049 crore, more than a three-fold increase from 1997-98. The increase in investment on mechanised trawlers and gill-netters are comparatively higher than other sectors. The capital investment on motorised sector also almost doubled from Rs.456 crore during 1996-97 to Rs. 861 crore during 2003-04. However, as expected, the non-motorised sector has shown a decline in investment from Rs. 923 crore during 1996-97 to Rs. 622 crore during 2003-04 in tune with their decline in production and diminishing returns. Further, substantial numbers of these units were converted into motorised units. In the open access marine fisheries, mode of ownership on means of production by fisherfolk greatly influences the occupational pattern and socio-economic status. The type and number of fishing implements owned is the yardstick to measure the economic well being of a fisher household. In India, hardly 13 per cent of the active fishermen in the marine fisheries sector have ownership on craft and gear in 2003 and another 3 per cent possess only gears. The proportion of owner operators in marine fisheries declined over the years with the increasing capital requirement for possessing motorized and mechanized fishing units. In the mechanised sector 12 per cent, The estimated gross capital investment on fishing motorised sector 9 per cent and traditional sector 21 per equipments alone works out to Rs. 4,117 crore at 1997 cent have ownership on crafts and gears. Most of the price level , in which 58 per cent is in the small scale non-motorised units are operating as family enterprises mechanized sector, 9 per cent in deep-sea vessels, 11 per not even realizing the operating cost of the labourers. cent in motorized sector and 22 per cent in non- Lack of finance and credit facilities does not allow these mechanized sector. It may be noted that out of the total fishermen to go for modernization and come out of the capital investments on fishing equipments, during 2003, vicious circle of poverty and low-income trap. Disguised 86 per cent is constituted by mechanised sector, 8 and 6 unemployment is rampant in capture fisheries and per cents respectively by motorised and non-mechanised fisherman need alternative avocations for their livelihood. sectors. The inter and intra sectoral migration also need to be The overall per capita investments of an active fisherman in 2003-04 was Rs.86,290 ranging from Rs.17,024 in the non-mechanised sector to Rs. 2,19,319 in the mechanised sector. During 1997, the overall per capita investment was Rs. 40, 363, where the investment per head in mechanised arrested for balanced and sustainable development of the coastal sector. Fishermen are in general unwilling to shift from fisheries sector for any other employment. Hence, mariculture is one of the most acceptable and viable occupations for coastal fisher folk. sector was Rs.1, 25,689, motorised and non-mechanised A report of the consultative group on international sectors invested Rs. 26, 835 and Rs. 13,979 respectively agricultural research states that within the next 15 years, per active fisherman in India. Further, fishing intensity is fish farming and sea ranching could provide nearly 40 per directly related with capital investment vis-à-vis number cent of all fish for the human diet and more than half of and type of nets they are possessing. A catamaran owner the value of the global fish catches. According to a report having different types of nets can have more number of of the FAO, the world aquaculture production is projected fishing days. If he is having only one type of net, he will to increase by 2.69 times by 2025 AD. India as a leading be having only lesser number of fishing days. In India, country in Asia in aquaculture production should be able 108 Central Marine Fisheries Research Institute From 14 - 23 December 2009 to achieve at least a production of 2mt (0.1mt finfish, The concept of Responsible Fisheries advocated by FAO 1.0mt crustaceans, 0.3mt molluscs and 0.6mt seaweeds) through its Code of Conduct for Responsible Fisheries is through mariculture by the year 2025 AD, i.e., 3.9 per an epitome among global efforts for realising the coveted cent of projected global aquaculture production of 51.8mt. goal of sustainable utilization of our marine resources. With improvements in the domestic market, The Code is a landmark in marine development thinking diversification of marine products exports, availability of as it represents the consensus achieved by more than a vast range of cultivable candidate species, several 150 nations across the world on the directions we should culture technologies and hydro climatic (or agro climatic) follow in order to avoid resource depletion due to irrational zones for coastal mariculture and sea-farming, India is utilisation behaviour pattern shown by various poised to become one of the world’s leading producers of stakeholders. Stock enhancement through artificial reefs mariculture products. and fish farming in the cages are better technological Issues related to Coastal Regulation Zone (CRZ), Integrated Coastal Zone Management (ICZM) and the options to counter problems of resource depletion. Scope for open sea mariculture unfounded apprehensions that coastal mariculture would adversely affect the environment, are leading to Prospects of Open sea mariculture unnecessary or avoidable litigations retarding the growth z Alternative source of income of the mariculture sector. It is worth to note that the z Better resource productivity z Entrepreneurship development z Societal empowerment lower and z Lower gestation period. present shrimp oriented, land-based coastal mariculture has resulted in the under-utilisation of the technologies developed for the culture of bivalves, seaweeds and pearls, and hence, requires being diversified and broad-based to take maximum advantage from the high production potential of tropical aquaculture farms. Problems of cage culture The information from various segments reveals that the z Lack of coherence among social groups z Issue of free rides among the commons versatile study on responsible fisheries observes that the z Problem of mute participation major factor that endangers its sustainable utilization is z lack of social commitment z Problems in revenue sharing system unanimously agreeable regulatory mechanisms. There are z Resource ownership issues many activities, which adversely affects the sustainability z Need for finding progressive fisher folk z Risk taker and innovator z Entrepreneurship development marine fisheries in India is currently undergoing through a phase of socio-economic cum ecological turbulence. A the open access nature of marine resources and the veritable lack of an enforceable property rights regime or of marine resources including shallow water mining, use of improper crafts, ghost fishing, destruction of mangrove forests, etc. Development processes such as urbanisation, industrial pollution and eutrophication of estuaries have also jeopardised the fragile ecological dynamics of the coastal area. The following interventions are required for promotion of cage culture 109 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi 1) Cages Participatory approaches for cage culture z Increasing the life of the cage z Sharing of accountability and responsibility z Cost reduction of the cage z Security for group conflicts and sabotage z Optimization of cage and mooring system z Institutional support in the event of uncertainties z Provision of subsidies for the cage construction z Reward for risk bearing z Encouraging a public private community participatory 2) Site selection and candidate species z Identification of congenial site considering the hydrographic and environmental parameters z Identifying location specific candidate species with better productivity inputs are required 3) Inputs approach There is enormous scope to enhance food fish production from the sea through mariculture. Adaptability of capital intensive fishing technologies in the capture fisheries will further escalate the cost of production and price of fish. Unlike land, water resource is not a limited factor of z Input standardization production for coastal states for adopting mariculture z Cost minimization practices. Hence, legislative support is vital for the z Revenue sharing approach promotion and propagation of open sea mariculture. It provides better option for enhancing the livelihood The other interventions are increasing density and revenue opportunities of the fisherfolk in the coastal sector sharing approach. without any migration. 110 Central Marine Fisheries Research Institute From 14 - 23 December 2009 Geographic information systems and site selection issues of open sea cage culture J. Jayasankar Central Marine Fisheries Research Institute, Post Box no. 1603 Ernakulam North P.O., Kochi - 682 018, Kerala jjsankar@gmail.com The GIS paradigm the core of earth are reasons for their pattern, the external As is much known in the Information Technology circles, environment like the atmospheric parameters and other a pair of numbers narrates the past, describe the present natural habitation like forests etc have a very important and in fact most importantly seal the future. The pair role in moderating their availability. Hence the idea of obviously means the latitude and longitude of the location viewing the geographic location as another latent cause any where under the sky. This perspective of referencing of expression of any important parameter alongside any type of information be it scientific, sociological, temporal references started clawing up on the ladders of psephological or economic, has taken the world of analysts and a whole new vista of analytical reasoning analytics by storm in past quarter of a century. The last emerged. That vista loosely named as analysis of geo- decades of the previous millennium were dotted with referenced series or spatial analytics has a very important spurt in methodologies and software which were totally requirement, a series of spatially referenced data spread dependent on this type of geo-referenced data. across temporal spectrum. The series of spatio- temporally Information collected serially over time, popularly known arranged data points are popularly referred to as as time series, always had a huge role to play in studying Geographic Information System or GIS in short. When the impact of changing eras and centuries at larger level originated the GIS concept was mostly applied to and seasons and cycles in shorter duration. The terrestrial references. The absoluteness with which the surreptitious shadow cast by the effect woven by time terrestrial data points could be uniquely referred by a pair on the trait of interest had always caught the imagination of geographic coordinates amply suited the development of analytical computational experts, especially of databases which were strongly rooted on those econometricians. Similar to the perpetual latent impact coordinates. Hence a plethora of application-ware were of temporal causes, the geographic factors also have been developed which led to the possibility of developing maps exhibiting impact on many an important scientific on the digitised geographic platform showing various phenomenon. Most of the natural resources available on intensities with which the parameters of interest were earth are bound to be impacted by their geographic available. These maps are popularly referred to as position on the earth’s crust. This is best explained by “Thematic Maps” and they formed an essential part of the availability of resources like ores and mines in certain many a dossier on resource spread, intensity and pockets on earth. Though geological reasons arising from availability. But GIS is much more than development of 111 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi thematic maps. The range of applications is multifaceted nucleus of marine GIS technology. It is quite constructive including geo statistics, modelling and development of to have stress on the importance of meta data while decision support systems. detailing the basic types of data on the very first occasion. Although terrestrial GIS has been quite in vogue in the The goal of marine GIS has always to be kept in mind past quarter century or so, the last decade saw the before trying to understanding the technical intricacies. emergence of another dimension to it, literally. The Marine Ranging from exploratory input to full fledged predictive Geographic Information System (MGIS) has the added paradigms, the MGIS has a huge chunk of goals which dimension of depth alongside the latitude and longitude. could be attained using specially drafted software. The It has been a much discussed and researched topic that core concepts of MGIS starting from location up to the marine fauna and flora demonstrate huge diffusion have strong relationship with various types of diversification down the bathymetric locales. Marine GIS information collected at various stages of the resource must first adapt to the characteristics of the marine world regeneration system. One standout example that could and marine data and the dynamic relations among the be cited is the association of regions using chlorophyll various components of the marine environment. Thus contents and sea surface temperature. Another way of MGIS opens up a new world of opportunity as well as looking at this whole paradigm is to pose self quizzing challenge which is 3 dimensional to say the least. queries and seeking answers like, “Where was it”; “How At this juncture the importance and utility value of 3D marine data sets as compared to the lat- long based terrestrial datasets have to be clearly understood. The depth component, needless to add, holds the key towards unravelling a huge treasure of wealth and its dynamics across the geographic vastness as well as their vertical upheaval. Such a three coordinate time series can always aid in shoring up the onerous task of studying the underlying interrelationships, trend, seasonality etc., which classically suit spatio-temporal analyses. Such a system can mutually embellish species life history data which in turn can aid in lucid portrayal of the progression down the prey- predator web. The interlinked nature of coastal, oceanic and fisheries information is for everybody to understand and study. The invaluable contribution that such a marine GIS can make while attending to the conflict between marine object dynamics and management policies is anybody’s guess. Another topic worthy of discussion is the type of input getting into a marine GIS including those obtained by meteorological gadgets as well as by Global Position Systems. A variety of technical disciplines and issues are associated with the long was it existing?”; “Is there any other resource abundant nearby?” etc. A model which satisfactorily answers the above asked questions would be the one which would be the best. MGIS and Oceanography GIS in general and MGIS in particular are affronted by Oceanographic concepts in many ways. The extent of influence can be well understood by the simultaneous consideration of micro scale turbulence to enormous gyres, both of whom have a serious role to play in shaping up the Information System. The role of Remote Sensing in these oceanographic data consideration has also been a topic of discussion and debate. Needless to say a management interface for coastal and oceanic environment is a much needed reality for any nation caring for justifiable exploitation of its resources. No better argument is needed for this aspect of exposition than the fact that 90% of pollutants generated by economic activities end up in coastal zone. It is a matter to ponder that the historic reasoning behind oceanic upheavals and their vulnerability to climate change which is a present day priority, have been comprehensively juxtaposed. The 112 Central Marine Fisheries Research Institute From 14 - 23 December 2009 inevitability of viewing the coastal zone from the artificial reefs which are bound to add strength and stakeholder’s point of view in the holistic perspective objectivity to the more publicized perception on GIS. rather than a fractured sector by sector basis can never Popular techniques like ecological modelling, scenario be under stated. building and vulnerability index computation on a geo Innumerable citations and references are available for the linking of oceanographic parameters with a MGIS Starting with datasets vis-à-vis their relevance to marine geology to information based accrued over hydrological sounding and multi-beam sonar systems, the review could be referenced platform have also been some of the much highlighted applications of MGIS. The MGIS is also a widely used tool to study and manage lesser focussed marine contingents like submerged aquatic vegetation, wetlands and watersheds. elaborate and informative Please refer V. Valavanis (2002) Literature is replete with initiatives taken by various for an excellent review. governmental and research establishments towards The role of GIS in flood assessment is another important facet full of references on digital elevation models, geographic flood information system and the world map of natural hazards. The citations available in Valavanis (2002) sufficiently sum up the efficacy and range of the tool. Oceanographic GIS. The developments in the Gulf, US and Europe have been worth chronicling (Valavanis (2002)). But the flagging of GIS as a solution to the ever increasing data volume and complexity should be approached with caution, as prima facie the statement indicates data redundancy and Information Systems target something primarily different. The issue of handling voluminous An exposition on the application of GIS in coastal and datasets usually target solutions in the mould of data oceanic management throws up interesting works like warehousing and Information Systems should not be Natural Resources Management Facility for Mozambique, equated with them. which primarily aim at social development like employment generation and poverty alleviation through participatory and sustainable management of natural resources. Certain attempts to rank coastal regions on their environmental sensitivity and pollution hazard with the help of GIS have also been discussed in literature. Throwing spotlight on yet another facet of GIS, work done by researchers across the globe by integrating hydrodynamics and morphometry are worth revisiting (Valavanis (2002)). The analytics done in describing a dynamic coastal zone like a lagoon ecosystems along with identification of main aspects of their degradation and identification of critical environmental parameters as also recovery plan will really spur the researcher towards seeking more on this application of GIS. In all there are around 20 unique efforts carried out at various locations across the globe till the turn of the last millennium Valavanis (2002). Most of the information systems mentioned are of very high environmental importance and their role in arriving t multidisciplinary answers to important scientific and societal queries can never be understated. Any logical extension of global examples of MGIS would be the focus on data sampling methods which broadly outlines the gadgetry involved in the collection of physical, chemical and biological data that add up to make the system. The point that commercial establishments have fanned out their research and analytical wings across the globe to sustain their interests through Oceanographic trend monitoring, is probably one single stand out fact. It There are multitudes of references on GIS application for effectively sums of the impetus being thrust on this study of oil spills in oceans, sea level rise and natural and branch of study and the enormity of changes and paradigm 113 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi shifts which are just round the corner. The information folk. Unlike hydrology and other physicochemical on various satellite sensors and the corresponding internet parameters, fish capture and availability based indicators sources are real highs which have augmented the reach have a very huge say on the holistic management of and purpose of MGIS. The development of other sources fisheries encompassing social, economic, technical, of remote sensed data like sensing platforms, Ocean Data ecological and ethical aspects. Any information system Acquisition System etc. is a meticulous collation on that has roots on this type of core information will have a advances in Oceanographic data sampling. Plethoras of whole lot of relevance and priority amidst its class of urls in the internet have comprehensive information systems. Naturally more criticisms and evaluations are regarding the details of the gadgets. bound to tow them. The Net is replete with references wherein umpteen instances of applications based on MGIS Another interesting issue discussed during the course of coming to the aid of fisherfolk and planners in various this topic is the one pertaining to real-time organisation countries. Interestingly another interesting aspect of the of marine survey data. Though it may sound similar to link between Information Systems and Fisheries is the the type of data integrations discussed so far to an role of geostatistics (spatial statistics) which is an innocuous reader, this throws up more light into the established branch of statistics inquiry into the geo integrated analytics that follow the online data referenced datasets. Albeit tools like kriging and accumulation. Hardware innovations like tape robot is variograms have been in vogue in the GIS universe they undoubtedly a fascinating interlude to this, but it has the are basically statistical tools which are adopted or adapted capability to derail a serious analytical researcher by to suit to the requirements of geo referenced datasets. leading him into the fascinating world of clustered data storage management. A large number of techno-administrative information consortia formed across the world catering to the fisheries This discussion could be rounded of with a detailed GIS (Valavanis (2002)). The chronological developments exposition on the methods and techniques adopted in that have taken place in the electronic documentation identification and quantification of gyres, classification and documentation of strides made by this branch of IT of surface waters, identification of temperature and are worth browsing through. The first GIS conference at chlorophyll fronts and tracking and measurement of Seattle in 1999 is a proof for this. While reiterating the upwelling. The mode of discussion is a judicious admixture intricacies involved in the comprehensive understanding of generic introduction followed by specific examples of of the relationship of fish and its environment, the the techniques application across the globe. The conference stressed that it is time to have a syndicated description of the unified efforts involved in the mapping effort to publish scholastic efforts in this direction. The of sea beds where local and remote methods of data statement – “The time has arrived for a Fisheries GIS derivation come to the fore cited in Valavanis (2002), could aptly wrap up the extensive discussion on GIS and its application in Oceanography. MGIS and Fisheries MGIS with a firm footing on various sources of information journal…” made by the participants (although it was made in early 2000’s) sums up the sincerity with which this document is prepared. Although the trickles which were chronicled in many publications have turned into a stream nowadays, an exclusive periodic publication of articles on GIS for marine fisheries is still elusive. is obviously well poised to have many applications in the The four stages at which GIS on fisheries can be utilised fisheries sector which have direct impact on the fisher are worth underscoring. Most of the planning and policy 114 Central Marine Fisheries Research Institute From 14 - 23 December 2009 compilers get saturated with the thematic maps and salmon fisheries were developed (Valavanis (2002)). The conceptual 3D output generated by GIS software. The discussion includes inclusion of environmental variables other stages viz. which area meets the set requirements, alongside the classical parameters like expanse of water presence or absence of a pattern over space and scenarios bodies etc. which gives a ringside view of initiatives made which can arise as a result of decisions and regulations in the first part of this decade. are weightier in purpose but less in vogue when it comes to utilisation. Hence it is mandatory for any discussion on adoption of GIS to equally stress all the four levels of the tool’s application. One important aspect to be highlighted on marine fisheries management through GIS is a citation of Senegalese case (Valavanis (2002)) which can be quite useful in the context of any similar footed nation. GIS was utilised to identify areas of conflict between artisanal and industrial fisheries and further proceeding on to the explanations for fisheries management on the degree of respect for the limits of regulated fishing areas and spatial fishing strategies as per the major seasons. The development of bioenergetic physiological principles augmented generalised spatial dynamic age structured multistock production model is a refreshingly new vista of GIS application in fisheries research. As another application of GIS in marine fisheries management, the mapping of biomes, large marine ecosystems etc. which go a long way in evaluating and explaining the distribution of marine features (e.g. primary production), which are not usually focussed upon under conventional studies can be mentioned. In a way there is an exhaustive collection of references which unravels all the possible utility areas of GIS in marine fisheries management (Valavanis (2002)). The use of remote sensing tools in the applied portion of data collation is another aspect of study. The grid construction and partial ground truthing of the remote recordings are all inseparable parts of this methodology and they can always be adequately described with the help of certain specific studies whose outputs like maps etc. have been provided (Valavanis (2002)). A list of more than 60 Internet sources of GIS databases embellishes the chapter and it has been one of the unique plus points of this book as such. A couple of snapshots from some GIS databases which include very pertinent theme maps like gear pressure on cephalopod populations in SE Mediterranean and catch areas of Octopus in the same area are excellent techniques to communicate with the starter Valavanis (2002). Developments like mapping of spawning grounds, essential habitats, migration corridors etc. which give a taste of how powerful and useful GIS can be in a fishery planner’s hand. MGIS and cage culture Open sea cage culture being an operation wrought with a lot uncertainties ranging from physical parameters of the ocean to the biotic and chemical factors affecting the morbidity and mortality rates of the animals to be cultured has to be necessarily based on informed plan. An informed The role of GIS in aquaculture needs no further emphasis plan is one where studied decisions are taken before the as it is almost similar to the terrestrial GIS wherein primary blue print is prepared which in turn are based on various role is in site selection. Herein come the issues of planning, parameters of concerned recorded pertaining to the area designing and execution of aquaculture assignments, of operation. Hence when the ocean can pose challenges apart from simulation backed economic forecasting tools, at least on three dimensions with a whole lot of physical which is a real plus for observers with less exposure. and chemical parameters on the tow. It is here the role of During the turn of last century some working models to manage and study thriving inland fisheries like freshwater a geo- spatial aggregation of parameters comes to prominence. 115 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Site selection for cage culturing exercises will involve specific inputs on the following parameters: (i) Bathymetry (ii) Currents (iii) Shelter and (iv) Water Quality Variations To explain this with an example to have a cage culture study based on Salmonids, it is essential to gather information on depth (m), current (m s-1), dissolved oxygen (mg l-1), salinity (%) and temperature (æ%C). From The drogues could be located at timed intervals from boats using sighing compasses. established literature inputs on the possible range and The fourth parameter of exposure could be categorised optimum values of these parameters might have to be by estimating wave heights at different locations. collected. Such data coupled with topography of the site Expected wave heights depend upon water depth and and exposure of the same would be used in the site wind velocity, duration of fetch over which wind passes assessment. before impacting the proposed location. Towards achieving this preliminary studies conducted in The wind data could be obtained from nearby weather the area focussed have to be collated and compiled. Then stations. suitable software to store/ update and analyse the data may have to be selected. This software could range from free to very cheap shareware to software meant for educational/ research institutions to full fledged commercial software like Arc GIS etc. As the next step the topography of the broader location where cage is The physico-chemical properties of the water like dissolved oxygen, temperature and salinity could be recorded at a number of fixed locations at different stages of tidal cycle using instruments like Oxygen meter and inductive bridge salinometer. planned to be set up along with the nearby coast details The whole database in GIS pertaining to the area under like bay etc should have to be mapped. The outline map focus should preferably be prepared in two scales which of the greater area like bay could well be a definitive are significantly different in resolution, something like 25 starting point. Suitably scaled maps have to be drawn x 25 metre block or 10 x 10 m block based. outlining the broader area of focus. In any typical GIS software the different types of The second task is to generate a bathymetric contour map information like outline map, points of observation, of the broader area of interest which could be achieved bathymetric data, current and exposure data are entered by making a series of boat transects at constant velocity in the form of different layers called grids. Usually the and bearing using echo-sounders. Depths such recorded base grid containing the blocks is kept transparent and could be plotted onto the base map. the other observed data sets are over laid on them either The third task of measuring the velocity of currents is as points or shapes or themes. done by using hydrographic drogues (sea anchors) Apart from these specific information that needs to be (displayed below). known for the type and size of cages, general information 116 Central Marine Fisheries Research Institute From 14 - 23 December 2009 of the broader area like pollution, availability of power For proceeding further the following are the parameters (electricity) and presence or absence of tourist-related estimated during the exercise. or ecological limitations. In the following series of pictures provided in the paper by Ross et al (1993) graphically explains the details of one such GIS mapping done to locate suitable ambience for Salmoid cages. (i) Mean depth : 6.8 m (ii) Current velocity : Upto 138 cm s-1 (iii) Speeds falling in acceptable range : 80% (iv) Nature of velocities: High at periphery; low near centre 117 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi 118 Central Marine Fisheries Research Institute From 14 - 23 December 2009 (v) Spatial interpolation: CURRINT over dependence of the precision of parameters estimated (vi) Dissolved Oxygen levels: 8.6 to 11.0 ppm (at high makes it overtly vulnerable to instrument/ equipment tide) ; 8.2 to 10.4 ppm (at low tide) (no difference errors. But one huge plus for this approach is the avoiding between surface and bottom readings) of individual bias and subjectivity while zeroing in on the (vii) Water temperature: 12.8C to 13,4 C and 12.9C to 13.0 C at high and low tide respectively. (well within the tolerance level) (viii) Salinity parameter: 19% to 29% location of choice. Still unfavourable locations can be removed at the outset by way of observing cage depth and limiting beyond 1.5 times of the depth. Such dictums like avoiding velocities less than 5 cm s-1 and those above 50 cm s-1 should be built keeping in mind the species to (ix) Wind speeds: 61 km h-1 and 85 km h-1 be cultivated. The sequences to be followed in the (x) Fetches observed 4.44 (NW), 3.42(NE) and 2.37 (NE) decision making process should be ceremoniously were the longest followed for any interchange of layers may produce (xi) Wave heights: 0.4 to 0.8 m different output. Based on the type of data collected over a reasonable With the advent of brutal computational power the period of time scorecard was prepared for the site process of decision making especially the computations selection. The scores with not more than two to three involved are of no big threat. But an assiduous selection outputs were decided based on the various parameters of decisive parameters and careful measurement of discussed above and the highest score is given to the parameters during survey is a must for any successful use blocks which have the most favourable parametric value. of MGIS technique for selecting Cage locations for Finally to decide on the suitable block (25 x 25 m) or (10 x 10m) the interpolated wave heights coupled with bathymetry will decide the score on the depth aspect. Similar recoding based on the scores for other parameters like water quality was conducted and the most ideal pocket was selected based on the pocket/ block which scored the maximum. (SUITABLE in the picture shown above). While this method seems to be straight forward and deeply rooted in the classical analytical traditions, the mariculture. References (i)Slater (1982). Learning through Geography , pp 340, Heineman Educational Books, Ltd, London (ii)Valavanis, V. (2002) Geographic Information Systems in Oceanography and Fisheries, London: Taylor and Francis, 2002, 209pp., USD $80, £45.00, hb (ISBN 0-415-284635). (iii) Ross, L.G, Mendoza, E.A and Beveridge, M.C.M (1993) The application of geographical information systems to site selection for coastal aquaculture: an example based on salmonid cage culture: Aquaulture. 112 pp 165- 178 119 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Economic analysis of cage culture of sea bass Narayanakumar, R. Central Marine Fisheries Research Institute, Post Box No. 1603 Ernakulam North P.O., Kochi- 682 018, Kerala, India ramani65@gmail.com Introduction return per rupee invested is the economic indicator that Open sea cage farming can be referred to as the method guides the investor to choose a particular enterprise or of culturing aquatic organisms in enclosed cages made of practice. Besides, the analysis of the economic various materials in the seas. The true cage farming is of performance serves as an indicator for the investor to recent origin and a well established practice in Southeast allocate his resources in the enterprises. This becomes Asian countries. The practice developed independently in very much essential, since the resources are scarce and a number of countries, all in Southeast Asia. Presently, the investor is interested to invest his scarce capital cage culture is developing fast and turning to a highly resource in that enterprise that gives the maximum return commercialized business activity in many Asian countries. for his investment. In India, pen culture and pond culture experiments were done The economic performance of the cage culture experiment along the southeast coast using the seed of rabbit fish, is worked out by calculating the annual fixed costs, groupers and sand whiting. Similar trials were also done along variable costs and the annual total costs from the cost Kerala and Karnataka coasts. In the recent years, open sea side. From the returns point of view, the harvest from farming was done at Visakhapatanam and cage/pen culture the cage, the gross revenue from the sales of the harvest experiments were conducted at Calicut and Vizhinjam is worked out. Using the cost and returns figures, the Research Centre of CMFRI (CMFRI Annual Report, 2006, 07). following economic indicators are estimated to test the economic viability and financial feasibility of any During 2008, fourteen cages were launched across the enterprise. east and west coasts. The failure witnessed in the launch of the first cage during May 2007, formed the stepping Table 1 Indicators of economic performance of the cage stone of success later in the same place. The lacunae in culture enterprise the launching of the first cage were rectified and Sl.No. Economic Indicators successfully re-launched during December 2007, which 1 Initial investment of the cage gave a substantial harvest of sea bass in April 2008. 2 Fixed cost (For crop duration of six months)a) Depreciation b) Insurance (2% on investment)c) Interest on Fixed capital (12%)d) Administrative expenses The success of the adoption of any innovation or new 3 Total Annual Fixed cost (A) technology lies in its economic performance. The rate of 4 Operating costsa) Cost of seedlingsb) Cost of feeding and other labour chargesc) Interest on working capital (6%) Economic analysis 120 Central Marine Fisheries Research Institute From 14 - 23 December 2009 5 Total Operating or Variable cost (B) 6 Total cost of production [Row(3)+Row(5)] 7 Yield of sea bass (in kg) 8 Gross revenue [(7) * Price per kg] 9 Net income [(8)-(7)] 10 Net operating income [(8)-(5)] 11 Cost of production (Rs./kg)[ (6)/(7)] The detailed economic analysis of the experimental cage 12 Price realized (Rs./kg) (8)/(7) culture practice demonstrated in Visakhapatnam (Andhra 13 Capital Productivity (Operating ratio) (5)/(8) Pradesh) and Balasore is given below to indicate how the assess their performance in Table 1. This will serve as the guidelines to the institutional agencies who are extending the financial support to the enterprise. Case studies The different economic indicators of the economic performance of cage culture enterprise are worked to economic analysis of the enterprise is done. (A) Visakhapatnam Table 2 Initial investment of the cage culture farm of 1061 m3 Sl. No. Items Investment (in Rs.) % to total Economic life (in years) 1 HDPE Cage frame 4,00,000 27.12 10 2 HDPE nets 3,00,000 20.34 10 3 Galvanized Iron Chains 80,000 5.42 10 4 Mooring equipments 60,000 4.07 10 5 Stone Anchors 1,50,000 10.17 50 6 Floats 1,50,000 10.17 10 7 Shock absorbers 25,000 1.69 10 8 Ballast 35,000 2.37 10 10 9 Ropes-HDPE 10 One time launching charges Total Initial Investment 35,000 2.37 2,40,000 16.27 14,75,000 100.00 Table 3 Details of Annual Fixed cost Sl. No. Details 1 Depreciation 2 Insurance premium (5% of investment) 3 Interest on fixed capital 4 Administrative expenses (2%) Amount (in Rs.) 1,16,000 73,750 1,77,000 29,500 Total fixed cost 3,96,250 Table 4 Details of Annual Variable cost of cage culture (for a crop duration of seven months) Sl. No. Details Cost % to total 1 Feeding 2,24,000 14.02 2 Seedling 1,50,000 9.39 3 Feed cost 9,00,000 56.32 4 Net cleaning 75,000 4.69 5 Underwater inspection 50,000 3.13 1.56 6 Net mending and Maintenance 25,000 7 Post crop overhauling 20,000 1.25 8 Security 1,00,000 6.26 9 Interest on working capital @6% for one crop duration Total 54,040 3.38 15,98,040 100.00 121 National Fisheries Development Board National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi Table 5 Economic indicators of the cage culture of Lates calcarifer Sl.No. Details 1 2 3 4 5 6 7 8 Annual fixed cost Annual Variable cost Annual total cost Gross revenue (after harvesting from 5th to 7th month) Net operating income Net income (profit) Capital Productivity (Operating Ratio) Annual Rate of return to capital Amount (in Rs.) 3,96,250 15,98,040 19,94,290 37,50,000 21,51,960 17.55,710 0.43 119% (B) Balasore economic parameters indicate that this open sea cage At Balasore, the initial investment for a 6m diameter cage farming of sea bass is economically viable. worked out to Rs.3,00,000. The fixed costs for the culture Conclusion period of six months was calculated at Rs.54,000. The Thus it is seen from the above results that the economic variable costs of the culture operation worked out to Rs. analysis of the experimental cage culture farm has worked 2,31,750. Thus the total cost of production to the out successfully with higher net operating income and net participants worked out to Rs.2,85,750 (Table 6). income in a crop period of seven to nine months. It is to be Table 6 Economic analysis of the experimental cage culture demonstration at Balasore Sl. No. Details of cost and returns 1 2 Initial investment for a 6m diameter cage Fixed cost (For crop duration of six months)a)Depreciation b)Insurance (2% on investment)c) Interest on Fixed capital (12%)d) Administrative expenses Total Fixed cost (A) Operating costsa) Cost of seedlingsb) Cost of feeding and other labour chargesc) Interest on working capital (6%) Total Operating cost (B) Total cost of production (Six months) Yield of sea bass (in kg) Gross revenue from 3032 kg Net income (8)-(5) Net operating income (Income over operating cost) Cost of production (Rs./kg) (6)/(7) Price realized (Rs./kg) (8)/(7) Capital Productivity (Operating ratio) (5)/(8) 3 4 5 6 7 8 9 10 11 12 13 Amount (in Rs.) 3,00,000 30,0003,00018,0003,000 54,000 50,0001, 75,0006, 750 2,31,750 2,85,750 3,032 5,75,760 2,90,010 3,44,010 94.24 189.89 0.50 The culture of sea bass yielded 3.03 tonnes of sea bass noted that once the practice is further expanded to many during the harvest conducted at the end of six months, areas and farms, the cost will decline due to the economies thus earning a gross revenue of Rs. 5,75,760 to the of scale of operation. Thus it could be concluded that the participants. The culture of sea bass earned a net open sea cage farming is a viable alternative and operating income of Rs. 3,44,010 at the end of six months economically & financially feasible mariculture operation and a net profit of Rs.2,90,010 at the end of the same for the stake holders to make use of. The State Fisheries period. The cost of production per kg of sea bass worked Departments and the Development Organizations like out to Rs.94.24 against the value realization of NFDB can promote the concept of cage culture on a large Rs.189.89per kg. The capital productivity measured scale with their institutional and financial support availing through operating ratio worked out to 0.80. These the technical expertise developed at CMFRI. 122 Central Marine Fisheries Research Institute

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Course manual: National training on cage culture of seabass, 14-23 December 2009

Course manual: National training on cage culture of seabass, 14-23 December 2009

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