Env Plg Marine Cage Fish

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Planning for Marine Cage Fish Farming following Coastal Zone Management Program
- Technological Options
Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Aquaculture Planning and Management, In the University of Hull

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Env Plg Marine Cage Fish

  1. 1. THE UNIVERSITY OF HULL Planning for Marine Cage Fish Farming following Coastal Zone Management Program - Technological Options Being a Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Aquaculture Planning and Management, The University of Hull, UK By Subir Kumar Ghosh   ¡ ¢ £ ¡ ¤ ¥ ¡ ¦ § § ¨ § © © ©
  2. 2. Contents Sl. No. Chapter Page No. SUMMARY 3 ACKNOWLEDGEMENT 4 1. INTRODUCTION 6 1.1 Background 6 1.2 Literature Review 9 2. METHODOLOGY 13 2.1 Objectives 13 2.2 Study Plan 13 2.2.1 Production Potentials 13 2.2.2 Assessment of Nutrient Load of Farming Systems 14 2.2.3 Comparative Economics of Farming Systems 14 2.2.4 Development Strategy 14 2.3 The Farming Systems 15 2.4 The Factors Influencing Nutrient Loading 17 2.5 Mechanical Waste Recovery 20 2.6 Biological Waste Recovery 21 2.7 Waste Quantification 22 3. RESULTS 23 3.1 Mass Balance Analysis 24 3.2 Production Potential Assessment 35 3.3 Economics 39 4. DISCUSSIONS 46 5. CONCLUSIONS 54 6. REFERENCES 56 7. FIGURES 59 2
  3. 3. Summary The increasing demand for food fish has led to increasing demand on aquaculture resources in terms land, water and inputs like energy and fish meal etc. Since aquaculture resource like any other resource is finite hence proper utilization of the resource needs to be based on sound principles of planning taking into account 1. Sustainable use of resource within the limits of ‘the carrying capacity of the environment’ 2. Selection of technology in terms of its nutrient loading and waste mitigation capacity, 3. Common resource use and 4. Economic return. The present assessment of the ‘Area Capacity’ of the Norwegian marine area in terms of aquaculture production is set on projected yield of 300 tons for cage volume of 12000 m3. The benchmark under reference is regulating Norwegian fish farming for nearly a decade while the emission levels has undergone sea change on account of development of new technology. The present study indicates the possibility of harnessing 600 to 3000 tons per unit, given the same cage volume as specified under the coastal zone management program called ‘LENKA’ by adopting the recent technological innovations without altering the benchmark in terms of nutrient loadings. Thus the technological innovations would put the given marine cage farming site to better use. It also makes a comparative study of the economic parameters such as cost of production, rate of return and sensitivity of the technological systems to anticipated risks. Thus a case is made out for sensitizing the planning process to environmental enabling potentials of the technological innovations. The planning process so developed besides permitting higher productivity could be used as a feed back control for generation of newer technology. Newer benchmarks for production could perhaps be set on the basis of newer nutrient emission levels. Thus short term goal could be set based on System2, medium term goal could be based on System3 and slightly long term goal could be set based on the outcome of the commercial trials of System5 adopting integrated fish-mussel-seaweed production. This system seems to be holding great promises in terms of not merely enhancing holding capacity but fulfilling such sustainability dimensions as ‘zero emission’, ‘resource generation’ and ‘integrated production’ beside being cost effective. If operationalised, the technology would render salmon farming truly sustainable. 3
  4. 4. ACKNOWLEDGEMENT At the onset I would like to mention that it was a difficult task to under take a study of this magnitude for the purpose of writing a dissertation towards fulfillment of the Postgraduate Degree program. Driven by my interest in this kind of work and the encouragement received from my supervisor I had ventured into this arena without realizing its implications. As may be evident it has taken little too long in completing the work. This is primarily due to the fact that this is one area where considerable research effort and consequent high volume of information generation has taken place in past two decades. Gathering this information besides being time consuming also proved to be somewhat expensive. Besides, the farming sites being located in the North Western part of UK, away from the city of Hull, did not permit frequent visit to the agencies involved in planning/implementation of this kind of projects and hence seeking answers to various doubts. Accessing industry related information also proved to be a difficult job. Within the framework of above constraints it was possible for me to deliver the results primarily because the University of Hull provided me the necessary extension of time to submit the dissertation and acceding to my repeated requests seeking extension of time. I am grateful to the University for providing me the most precious input in this project by allowing the extra margin of time. I am highly obliged to the University for this. I am sure that given the resource at my disposal, it would not have been possible for me to meet the required fund for undertaking my study tour to Scotland for the purpose of visiting the farming sites, the various institutions connected with planning, development, and R & D pertaining marine cage fish farming. The University made this possible by granting me the travel fund. This was a very kind gesture for which I am and shall remain indebted to the University for all times. I sincerely thank all those persons who made this possible. As already indicated, the work required considerable inputs by way of relevant information and literatures. Besides being expensive, it was time consuming and required lot of support from the HIFI as well as the University library in arranging them through the facilities extended by the British Library network. I thank the University Library for their excellent support. I am extremely thankful to my Department in general and to Mr. Stephen Ridgway and Dr. Kevin Crean in particular for extending liberal assistance using Departmental resource. I would also like to thank Dr. K. Haywood for his encouragements. The person to whom I owe the success of this project is my Supervisor Mr. Ridgway who has been a constant source of encouragement. I am grateful to my employer, The National Bank for Agriculture and Rural Development (NABARD), for granting me Bank’s scholarship for higher studies without which it would not have been possible for me to pursue higher studies in UK. I most humbly acknowledge the confidence imposed in me by the Bank and dedicate this dissertation to The National Bank for Agriculture and Rural Development, Mumbai. I have received considerable first hand information related to my area of study from the following organizations: 1. Marine Harvest McConnell Farms Office, Blar Mohr, Fort William 2. Highland Council Planning Dept., Inverness 3. Scottish Environmental Protection Agency, Fort William 4. Sea Fish Industry Authority, Ardtoe, Acharcle, Argyll 5. Institute of Aquaculture, Stirling University, Stirling 6. Stirling Aquaculture, University of Stirling 7. The Crown Estate, Edinburgh 8. The Scottish Natural Heritage, Edinburgh. I am thankful to all these institutions for 4
  5. 5. providing me necessary information and helping me in carrying out my project. My special thanks goes to Ms. Judy O’Rourke of the Sea Fish Industry Authority, Ardtoe, without whose help my visit to Ardtoe would not have materialized. I take this opportunity to thank her for the excellent logistic and library support. I acknowledge the help received from Marine Harvest McConnell Farms Office, Blar Mohr, Fort William in showing me the farm and providing economics related information. I acknowledge with a deep sense of gratitude the help and guidance received by me from Dr. Arne Ervik, whose work on the concept of MOM system had provoked me to take up this work. I am grateful to him for giving me patient hearing and offering valuable suggestions. I am grateful to him for introducing me to the works of Prof. Hans Ackefors, on nutrient emission, which has been used by me extensively in this project. My thanks go to Prof. Ackefors for sending me his publication on environmental impact of different farming technologies. The suggestions given by Dr. Beveridge were very useful in restricting the nature of the project work given the limitations. I am highly thankful to Dr. John Bobstock of Stirling Aquaculture for giving me hearing and providing me industry related information. I am thankful to Mr. Øivind Hatteland, Export Sales Manager, AKVA for sending me a copy of the KPMG publication, which was very handy and informative. It would have not been possible for me to pursue my studies in UK had it not been for the sacrifices of my loving wife Soma, who took upon herself the reign of the household during the long period of my absence. I doubt whether I could have ever completed this dissertation (being away from my family) but for the support from my sister-in-law (Madhumita Ray) and my co- brother (Sunirmal Ray). I am highly indebted to both of them for their co-operation and help. 5
  6. 6. Planning for Marine Cage Fish Farming following Coastal Zone Management Program – Technological Options (Being a Dissertation submitted in partial fulfillment of the requirements for the Degree of Master of Science in Aquaculture Planning and Management) INTRODUCTION Background The increasing demand for food fish has led to increasing demand on aquaculture resources in terms land, water and inputs like energy and fish meal etc. Since aquaculture resource like any other resource is finite hence proper utilization of the resource needs to be based on sound principles of planning taking into account 1. Sustainable use of resource within the limits of ‘the carrying capacity of the environment’ 2. Selection of technology in terms of its nutrient loading and waste mitigation capacity, 3. Common resource use and 4. Economic return. Aquaculture and Global Food Fish Supply One of the most important challenge before mankind is to meet the food for the increasing billions especially, more so in the context of the present scenario of declining agricultural production. The world population has grown from two billion in 1950 to the present level close to six billion. It is expected that our population on this planet is going to be 8.5 billion by the year 2025 and 10 billion by the year 2050 and may stabilize around 12 billion (FAO, 1998). The growth rate of world agricultural production is slowing down. From an annual rate of about 3 percent in the 1960s, it dropped to about 1.6 percent during the decade 1986-1995 (mainly because of the drastic production decline in countries formerly comprising the USSR) and is expected to be in the order of 1.8 percent for the period 1990-2010. (FAO, 1998). A different situation is true for the fisheries sector, production increased at a compound rate of 3.4 percent per year in the period 1960-1990, and this growth rate has been maintained over the past decade. During the last 15 years, this growth has essentially been a result of the rapid increase in aquaculture output, which recorded an annual increase of 11.8 percent in the period 1984-1996 (FAO, 1998). The global fish production in 1996 had reached the level of 110 million metric tons (mt) of which the contribution of aquaculture production was 26.3 tm comprising of 15.6 mt from inland sector and 10.7 mt from marine sector respectively This is excluding the production of aquatic plants, which amounted to 7.7 million tons in 1996 (FAO, 1998). Globally, landings of marine fish are continuing to level off, the annual growth rate having fallen from 6 percent during 1950 –1983 to 1.5 percent during the following decade to 0.6 percent during the 1995-1996 biennium. This is also the general trend for most major inland fishing areas of the world which faces a 6
  7. 7. constant threat from increase in the loss and degradation of land, forest resources, biodiversity and habitat as well as the growing scarcity and pollution of freshwater (FAO, 1998). Thus keeping in view the burgeoning population growth and the consequent rise in food fish demand, which is projected to increase from the present level of 84.5 mt to 114.8 mt in 2025, a demand supply gap of 28.5 mt needs to be addressed. The above gap can only be bridged by augmenting production in the aquaculture sector (Ackefors, 1997). Aquaculture provided 20 percent of global fisheries production (and 29 percent of food fish) in 1996. The potential of aquaculture to meet the challenges of food security and to generate employment and foreign exchange has been clearly demonstrated by the rapid expansion of this sector, which has grown at an APR1 of almost 10 since 1984 compared with 3 for livestock meat and 1.6 for capture fisheries production (FAO, 1998). Such rapid growth of aquaculture has generated a number of environmental and resource use conflicts suggesting that the present form of aquaculture development is not sustainable and that there is need for environmental planning based on the principles of sustainability. Sustainable Delopment Sustainability is the dynamics of growth in a finite world. On the road to development, mankind has crossed two important milestones, which has shaped its existence on this planet. The first was ‘The Agricultural Revolution’ of the Neolithic period and the second, ‘The Industrial Revolution’ of the past two centuries. Both the revolutions were associated with productivity to meet growing human needs and demands. In the process of development it has used the natural resources, both renewable and non-renewable to produce goods and services. The success of both the revolutions at the end has led to scarcities whether in terms of pressure on land and water or in terms of fuels and minerals, which can be attributed to finiteness of the resources on one hand and the increasing demand from a rapidly growing population on the other. To add to the misery, the process of development has generated a cost viz. ‘the pollutants’. It has been stated that in our efforts to meet growing human needs, we draw too heavily, too quickly, on an already overdrawn environmental resource account. They may show profit on the balance sheets of our generation, but our children will inherit the losses. Thus as per the Brundtland Report, “sustainable development is the development that meets the needs of the present without compromising the ability of the future generations to meet their own needs”(UNWCED 1987). It is now clear that the planet has a capacity to withstand the impacts of development i.e. it has a capacity to produce - ‘the Limit’ and a capacity to absorb and assimilate the fall outs of development - ‘the Carrying Capacity’. Thus any activity within the limits of ‘limit’ and ‘carrying capacity’ could be carried out on a long-term basis without threatening our existence and was termed ‘Sustainable’ - giving rise to the concept of ‘Sustainability’. The above issues apply to aquaculture sector as well wherein environmental planning is based on the concept of i. Capacity to produce and ii. Capacity to absorb and assimilate the wastes. The environmental economists refer to this as the capacity of natural systems to provide ‘natural capital’ (as ‘source’, ‘sink’ and ‘service’ provider). Thus the ability of natural systems to provide energy and materials, and to absorb the interference of pollution and waste, is the critical threshold within which the world economy can expand. 7
  8. 8. The ecological perspective of sustainable development is based on the concept of ‘carrying capacity’ i.e. the maximum impact that a given ecosystem can sustain, which has been put forward in the following words (Meadows, 1992): “The maximum population that can be supported indefinitely in a given habitat without permanently impairing the productivity of the ecosystem(s) upon which that population is dependent. Thus in order to be sustainable, the level and rate of natural resource depletion and pollution emissions should be no greater or faster than the level and rate of regeneration or absorption of environment systems”. The FAO defined it as: ‘Sustainable development is the management and conservation of natural resource base and the orientation of technological and institutional changes in such a manner as to ensure the attainment and continued satisfaction of human needs for present and future generations. Such sustainable development (in the agriculture, forestry and fisheries sectors) conserves land, water, plant and animal genetic resources, is environmentally non-degrading, technically appropriate, economically viable and socially acceptable’ (FAO, 1996). Thus sustainable development related to aquaculture would mean conservation of natural resource; technological soundness in terms of waste generation and waste mitigation, economic viability and its social acceptance. While the conservation of natural resource and social issues related to common resource use have been addressed by the existing environmental planning process by many workers in the field, the issues pertaining technological soundness and economic viability have not been integrated into the planning process. Thus environmental issues have attracted the attention of many research workers in the field (e.g. Ackefors et al.1979; Gowen et al.1987; Rosenthal et al 1988; Ackefors et al. 1990; Gowen 1994). The discharge of nutrients and wastes from aquaculture has been regulated through legal measures in many countries (Ackefors and Olburs 1995). The need for carrying out aquaculture in environmentally sustainable, socially acceptable and in harmony with principles of common resource use, has led to the formulation of integrated coastal zone management plan by the coastal states as a follow up of 1992 United Nations Conference on Environment and Development, in Rio de Janeiro, Brazil. There is competition for sites and water resource in the coastal zone between aquaculture and other users viz. agriculture, shipping, tourism, salt manufacture, harbors, aqua park etc. (Chua, 1992). To address such environmental issues on a regional scale, the concept of ‘holding capacity’ was developed to denote maximum aquaculture production attainable in a water body without eliciting an unacceptably high degree of environmental change. Several models have been developed for determining the response of standing water to nutrient loading for lake management and the same have been modified for use in cage fish farming (Beveridge 1984; Weston et. al.1994). Mass balance models was developed by Vollenweider (1968), which was modified by Dillon and Riger (1974) and adapted for cage culture by Beveridge (1984). This mass-balance equation is based on movement of phosphorus compounds through a lake system. Such models have been useful in Scotland for environmental impact assessment and management of freshwater lakes for aquaculture. There were some attempts to quantify holding capacities for salmonid culture in marine and brackish waters based on nutrient loading (H6kanson and Wallin 1991) and oxygen consumption 8
  9. 9. of solid wastes (Aure and Stigebrandt 1989). Both of these models had their limitations having been developed for specific environments and not applicable for predictive value elsewhere. In order to deal with the environmental issues owing to rapid growth of the salmon industry in Norway coast a national program called ‘Nation-wide Assessment of the Suitability of the Norwegian Coastal Zone and Rivers for Aquaculture’ (LENKA), was started in 1987 and was completed in 1990 (Ibrekk 1993). The planning was based on the assessment of the ‘holding capacity’ of the coastal waters and integration of aquaculture with other coastal activities through identification of suitable coastal habitat for cage farming of salmon and subjecting the same to the ‘holding capacity’ of the site taking into account overall nutrient loading from all existing as well as proposed activities in the area. The next step in the direction of coastal zone management has been the development of ‘Modelling-On growing fish farms-Monitoring’ (MOM), which is a management system used to adjust the local environmental impact of marine fish farms to the holding capacity of the sites. The concept is based on integrating the elements of environmental impact assessment, monitoring of impact and environmental quality standards into one system. Thus it may be evident that the present direction of research /development covering environmental sustainability of marine aquaculture has taken into account the ‘carrying capacity’ of the coastal area as well as the ‘holding capacity’, accounting for competitive use of coastal resource by common users while integrating them into one common management plan. Following this it may be possible to spell out a development plan for aquaculture in a given marine area based on the level of nutrient loading by the cage farming practice of salmon in vogue. However it may be possible to develop alternate production plans for the same marine area considering available technologies with different waste reduction and mitigation efficiency and their economics of operation. It has been indicated that reduction in feed wastage by 30% would increase the potential of aquaculture by 6-8 % and in areas of high level of aquaculture activity such as Hordaland, the effect would be even greater (Ibrekk 1993). The strategy for such planning could be 1. Maximizing fish production based on existing pattern of nutrient loading from a given area, 2. Maximizing production within overall ‘carrying capacity’ limit using least polluting technology, 3. Maximizing return from a given area by adopting least cost production system thereby improving profit margin or 4. a combination of one or more of the above interests. Thus it may be necessary to look into the waste mitigating efficiency of the farming technology and the economics of production of salmon using these while working out a coastal zone management plan. The present exercise is a step in this direction to study the impact of the above elements on decision making if introduced into the existing Norwegian planning based on LENKA. The present assessment of the ‘Area Capacity’ of the Norwegian marine area in terms of aquaculture production from marine cages fish farming is not technology sensitive. It is based on the nutrient loading from traditional cage farming system of salmon with a projected yield of 300 tons from using conventional feed with FCR of 1.5 and accordingly setting the ‘Area Capacity’ norm. Thus it may be possible to improve the production plan by incorporating suitable technological innovations. 9
  10. 10. Brief Literature Review There is increasing dependence on aquaculture as a food source for meeting the increasing protein requirement of the burgeoning world population (FAO 1998, Ackefors 1997, Baird et al. 1996). Intensive cultivation of marine fish species has substantially increased in last two decades resulting in increased interaction between fish farming and the environment (Rosenthal et al.1987, 1988; Gowen et al. 1989; Hall et al.1990, Weston 1991, Iwama 1991, Phillips et al.1990,1993 and Weston et al.1994). Of the different types of coastal aquaculture, intensive production has the greatest potential to generate waste. It has been estimated for example that production of 100 tons of salmonids with a feed conversion ratio of 1.5, could result in annual loading of 1 ton of total phosphorus; 97 ton of total nitrogen and approximately 50 ton of organic matter (Ibrekk et al. 1993). The effects of marine fish farming on the surrounding marine areas have been discussed by many authors (Braaten et al.1983, Beveridge 1984, 1996, Holmer 1991 & 1992, Holmer et al. 1996 and Gowen et al.1987). The wastes from the coastal aquaculture operations has the potential to enrich aquatic eco-systems (Aure & Stigebrandt 1990 and Aure et al.,1988), particularly when farms are located in semi-enclosed bays, which have restricted exchange (GESAMP 1996). The major impact has been observed on the benthic macrofauna (Brown et al.1987; Ritz et al. 1990; Weston, 1990; Headerson et al.1995 and Pearson et al. 1983) as well as physical and chemical change in the sediments (Brown et al.1987; Coyne et al. 1994 and Gowen et al. 1988). The most important benthic impacts include azoic sediments (Brown et al.1987, Weston 1990 and Tsutsumi et al. 1991), anoxic sediments (Hall et al.1990, Holmer & Krisstensen1992, 1996, Hargrave et al. 1993 and Wu et al. 1994) out gassing of methane and hydrogen sulphide (Samuelsen et al. 1988, Wildish et al. 1990a). Thus considering the negative environmental impact of marine cage fish culture, a need was felt for proper site selection, assessment of the capacity of any given marine area to withstand environmental loading and its integration in the coastal planning based on common resource use and social acceptance. As a first step to address such environmental issues on a regional scale, the concept of ‘holding capacity’ was developed to denote maximum aquaculture production attainable in a water body without eliciting an unacceptably high degree of environmental change. Several models existed for determining the response of standing water to nutrient loading for lake management and the same were modified for use in cage fish farming (Beveridge 1984; Weston et al. 1994). Mass balance models was developed by Vollenweider (1968), which was modified by Dillon and Riger (1974) and adapted for cage culture by Beveridge (1984). This mass-balance equation is based on movement of phosphorus compounds through a lake system. Such models have been useful in Scotland for environmental impact assessment and management of freshwater lakes for aquaculture. There were some attempts to quantify holding capacities for salmonid culture in marine and brackish waters based on nutrient loading (H6kanson and Wallin 1991) and oxygen consumption of solid wastes (Aure and Stigebrandt 1989). Both of these models had their limitations having been developed for specific environments and not applicable for predictive value elsewhere. The application of Geographical Information System to site selection for coastal aquaculture has also been developed (Ross et al.1993). Issues related to resource planning and management of 10
  11. 11. coastal aquaculture have been discussed at length (Baird et al.1996). In addition to environmental and biological issues, the social and economic issues have been integrated in coastal aquaculture planning (Chua et al.1989, 1992 & 1993; GESAMP 1991a; Barg 1992 and Pullin et al.1993). A number of methods have been proposed and used for identifying and evaluating environmental impacts. United Nations Economic and Social Commission for Asia and the Pacific short-listed eight methods (ESCAP, 1985b). Each method has its advantages and disadvantages, and the best known are the checklists, matrices and networks (Pillay 1996). The main drawback with the checklists are that they do not provide any guidance on the ways an environmental component may be affected by one or more development features (Pillay 1996). The matrices suffer from the drawback that they focus on direct impact between two items, and result in compartmentalizing the environment into separate items. The cumulative impacts through different pathways are not evaluated. The network method addresses this problem and traces the causes and effects of the relevant factors however, it does not evaluate the magnitude of the impacts and also does not propose alternative projects (Pillay 1996). The situation arising out of competitive use of the coastal zone by growing users has necessitated regulation of the activities through coastal zone management. As per GESAMP (1996), Coastal Zone Management needs to ensure that ecological change does not exceed pre-determined and acceptable levels, for which a management framework is adopted prior to development that would include the establishment of Environmental Quality Objectives (EQOs) and Standards (EQSs). The framework is also expected to offer scope for an Environment Impact Assessment (EIA) and a Monitoring Program. A coastal zone management programme called LENKA (Nationwide Assessment of the suitability of the Norwegian Coastal Zone and Rivers for Aquaculture) was started in 1987 and ended in 1990. The program developed an efficient and standardized tool for coastal zone planning. The program is based on a methodology for assessing the suitability of marine areas for aquaculture. The marine areas holding capacity is determined by a developed model which is based on (1) an assessment of the maximum acceptable organic loading of the marine areas and (2) an assessment of the area available for aquaculture development (Ibrekk et al. 1993). Several projects have been initiated to improve the accuracy of the LENKA. a mathematical model called “Fjordmilφ”, has been developed (Ibrekk 1993), which gives a quantitative estimate of eutrophication effects of fish farming in fjords. The model gives a quantitative estimate that is considered to be more reliable than the indices used in the LENKA model. The next step in the direction of coastal zone management, site selection for marine fish farming and environmental protection, is development of another concept of management system called MOM (Modelling-On growing fish farms-Monitoring), which is designed to maintain satisfactory environmental conditions in and around fish farms and may be a valuable tool in site selection and coastal zone management. It is directed towards adjustment of the local environmental impact of marine fish farming, specific to the conditions of culture practice and the holding capacity of the sites. The concept is based on integrating the elements of environmental impact assessment, monitoring of impact, and environmental quality into one system (Ervik et al.1997). This forms the core concept on which is based the management framework of GESAMP (1996) discussed earlier. The MOM concept although deals with the local environment impact of marine fish farms, has a functional overlapping with LENKA as regard monitoring of impact in the regional impact zone 11
  12. 12. is concerned. The precise monitoring of the impacts under MOM would provide an opportunity for better assessment of holding capacity under LENKA. The following applications for the MOM system have been advocated (Ervik et al. 1997). 1. Simulation of environmental impact of a fish farm on a given site. 2. Adjustment of farming practices to prevent impact from exceeding the EQSs. 3. Assessment of relative differences between sites in terms of holding capacity. 4. Assessment of relative differences between various arrangements of net cages in terms of nutrient loading and dispersion. 5. MOM could be used in conjunction with LENKA for Coastal Zone Management. Sustainable marine farming system also need to address the problems imposed by availability of feed stuff such as the stock of pelagic fishes upon which, the fish meal industry is based ( Baird et al. 1996). Given the holding capacity of a marine area, there may be alternatives in terms of technology of cage fish farming to select from. It is logical to conclude that such alternatives involving improvement in terms of nutrient loading, waste recovery and nutrient recycling would put the given marine cage farming site to better use. It would thus permit comparative assessment of holding capacity of a given marine area, cost of production and economics of operation in terms of technological development. 12
  13. 13. Methodology The Objectives The present study has been designed to study the following issues: 1. Assessment of nutrient loading from five selected salmon farming technologies using different type of feed, feeding technique and waste recovery mechanism. 2. Comparative assessment of production potentials of representative Norwegian marine sites deploying alternate farming systems. 3. Comparative assessment of the cost of production and economics of salmon farming following the five different production techniques. 4. Utilizing the nutrient loading and economic performances of the production systems in drawing up strategy for coastal zone planning addressing one or more of the following issues: i. maximizing fish production using least polluting technology, ii. maximizing return from a given area by adopting production system generating maximum profit margin iii. adopting least cost production system for a better market share of the product. The Study Plan 1. The Production Potentials Comparative assessment of production potentials of representative Norwegian marine sites deploying alternate farming systems falling in ‘A’-category zone in Northern Norway using alternate technologies has been attempted. These technologies offer varying scope for reduction in nutrient loading and waste recovery. Production potentials of Norwegian coastal zone as assessed under the LENKA system (Ibrekk, 1993) has been considered. The traditional farming system with defined nutrient loading and production potential provides the bench mark for assessment of ‘Holding Capacity’ and ‘Area Capacity’ of the Norwegian coastal waters, and the same has been adopted here for assessment of the production potentials using alternate farming technology. The ‘Holding Capacity’ assessment is based on nutrient loading from salmonid farming, general knowledge of the marine environment and detailed studies of areas with intensive aquaculture activity (Aure and Stigebrandt 1989). The ‘Area capacity’ is primarily calculated based on the marine area in a zone available for aquaculture, excluding areas unsuitable for aquaculture and areas already used or reserved for other purposes. The net area is converted to production potentials using the standard set for Norwegian waters (Ibrekk, 1993). The ‘Area Capacity’ so assessed is matched with the ‘Holding Capacity’ and lower of the two values would determine the gross available capacity for future planning (Figure 1). Thus as may be evident, the production potential is key to the assessment of ‘Holding Capacity’ and ‘Area Capacity’ of the marine sites and the same has been quantified based on average fish farm’s standard production of 25 kg /m3 (300 tons of fish produced per 12000 m3). With a feed 13
  14. 14. conversion ratio of 1.5, annual loading from an average farm has been estimated to be 3 tons total phosphorus, 27 tons total nitrogen and approximately 150 tons of organic matter (Ibrekk, 1993). It is expected that the production potential would undergo upward change with reduction in nutrient loadings. This in turn would enhance the Area Capacity’ and the ‘Holding Capacity’ and the consequent ‘Gross Available Capacity’ for future planning. 2. Assessment of Nutrient Load Discharge of nutrients and organic material is inevitable in open cage system. The main factors involved in the process are 1. the volume of production, 2. the feeding technology, 3. the quality of feed and 4. the waste mitigating measures deployed. Hence a comparative analysis of nutrient loading for the following salmon cage farming systems was done using available data. • Traditional Farming System using conventional feed and feeding mechanism • Improved Farming System using efficient feed and feeding mechanism • Improved Farming System using HND feed and efficient feeding mechanism • Farming System using efficient feed and Lift-up feed collector • Closed Bag Integrated Farming System The systems under reference differs from the point of view of factors influencing nutrient loading. The factors influencing nutrient loading are as under. • Feed quality • Feeding method • Waste recovery • Nutrient recycling (Biological Waste Recovery) The factors influencing nutrient loading have thus been taken into consideration in the present study through selection of the above technologies. These factors influencing the nutrient loading are discussed followed by methodology for assessment of the waste loading . 3. Comparative Economics The cost of production of salmon was worked out following the Norwegian case studies on Atlantic salmon (Bjdrndal 1990) and information collected during field study conducted in connection with the present project work. The comparative economics of the farming systems under consideration was studied using discounted cash flow technique as developed by the Economic Development Institute, International Bank for Reconstruction and Development (Gittinger 1981). 4. Development Strategy The variations in nutrient loading between the farming systems have been utilized to assess their production potentials. Selection of the least impact farming system is expected to result in maximization of production from a given marine area with known holding capacity. 14
  15. 15. The comparative study of the IRR of the farming systems would provide an opportunity to maximize return by proper selection of technology with or without maximizing production. Least cost production is an important criteria in marketing the product and hence an assessment of this parameter is necessary. Even though we may hit upon a least polluting farming system however its applicability would be ultimately determined by the marketing factor such as cost of production. The Farming Systems i. Traditional Farming System using conventional feed and feeding mechanism (System 1) Considering the Norwegian regulations, farm size of 12000 m3 has been considered with overall production limit of 300 tons. A wide variety of cage designs has been developed over the last 20 years; however, the common features are a floating collar, usually rectangular, a suspended net bag and a mooring system. In the present study steel cage system has been considered (Fig.2a & 2b). The design of cage which is frequently used in Scottish and Norwegian farms, comprises a square or rectangular frame of cage superstructure with walkways in between rows of cages. A steel handrail about 0.75m high, is attached to the inside of the walkway, and from this, the cage bag is suspended. Typically, the cages are connected to each other with ropes and shackles to form a floating rectangular raft of 15-20 individual cages with a central walkway. The raft is moored to the sea bed or to the shore using anchors, chains, ropes and shock-absorbing systems. In the present case 16 cages with cage volume of 800 m3 each have been considered of which 15 would be under production with one stand-by cage. Thus the effective production volume is estimated to be 12000 m3. Considering a stocking rate of 7.5 smolt / m3, 85% survival and an average harvest weight of 4kg salmon, the final harvest is expected to be 300 kg. The production is based on the assumptions under ‘LENKA’ system. The feeding system is considered to be automatic feeder type based on a feeding program pre-set by the farmer to dispense dry pellet as discussed subsequently. A 12V battery and a control unit connected through cabling along walkways and cage superstructure can regulate feeding in number of cages adopting centralized feeding. Feeding is synchronized in all the cages using the timing device. In the traditional Farming System use of conventional feed with FCR value of 1.5 (‘N’= 8%; ‘P’ = 1%) has been considered corresponding to nutrient loading under ‘LENKA’ system. ii. Improved Farming System using efficient feed and feeding mechanism (System 2) The farming system is similar to the earlier system excepting for the feeding system, type of feed used and the production program. In this system improved feed with FCR value of 1.0 (‘N’= 7.5%; ‘P’ = 0.9%) has been considered. A strict feeding regime is envisaged using computer aided ‘Adaptive Feeding System’ that controls automatic feeders by accurately matching feed delivery to fish appetite. The Aquasmart AQ1 with advanced sensor, communications system and software is one such system with which an entire farm can be monitored and controlled from a 15
  16. 16. centrally located PC (Fig.3). This enables minimising feed loss to the extent of 4% of total nutrient supply. The production program is based on the production potentials of such cage systems under Norwegian conditions as described by Bjdrndal (1990). Accordingly a cage volume of 12000 m3 is expected to produce 370 tons of fish, stocked at the rate of 10 smolt/ m3 with 15% survival and average weight of 3.7 kg/fish. iii. Improved Farming System using HND feed and efficient feeding mechanism (System 3) The farming system is similar to the earlier system excepting for the type of feed used. In this system high energy nutrient dense diet with FCR value of 0.83 (‘N’= 7.2%; ‘P’ = 0.9%) has been considered. The low-protein, high-fat composition of these feeds with protein sparing effect is expected to reduce protein catabolism and utilize the same for anabolic process thus improving FCR while reducing excretion of nitrogenous products. A strict feeding regime is envisaged using computer aided ‘Adaptive Feeding System’ as in the case of the earlier system. The production program is also similar to the previous system. iv. Farming System using efficient feed and Lift-up feed collector (System 4) The Lift-up Kombi system is provided with a fine meshed funnel shaped net cloth, which is provided under the cage to which a tube is attached at the bottom to remove dead fish, excess feed and large faecal particles. These are collected by lifting the water from the bottom of the cage using the water lift and passed through the filtration unit that retains the particulate matter. The Lift-up Kombi system is known to collect upto 100% surplus feed, sized 6 mm and larger and nearly 70% of 4 mm particles (Ervik et al, 1994). The description of the system is presented subsequently. From the farming system point of view it is similar to system2. It is based on use of the same feed and feeding system as well as production programme as in system2. The additional feature being the reuse of waste feed and removal of particulate faecal matter. v. Closed Bag Integrated Farming System (System 5) The concept of clean technology is based on principles of waste removal deploying biological process that would take care of the particulate matter and the dissolved nutrient, generated on account of uneaten feed, undigested feed and excretion. Integrating farming of mussels and seaweed with fish is known to be very effective in recycling nutrients and wastes. In fact such floating enclosed system has been developed and tested in full-scale for the last 8 years in Norway. A theoretical model linking the production of salmon, blue mussel and seaweed in floating enclosed unit was performed during 1992-94 to minimize eutrophication from fish farming activities (Bodvin et. al.1996). Detail description of the model is discussed subsequently. The model plant is based on production data from a full-scale pilot farm built in Flekkefjord (Skaar & Bodvin, 1993) as described by Bodvin et.al. (1996). The standard plant with production volume of 6000 m3, consisting of 12 fish units, each with a volume of 500 m3is linked to 12 mussel units which in turn is linked to 12 seaweed units. The fish unit with stocking rate of 15 smolt m3 and 85% survival is estimated to produce 300 tons of fish. In order to trap the particulate emissions from the fish unit 1350 tons (fresh weight) of mussel is required. The dissolved outflow from the fish unit as well as the mussel unit is estimated to support 3000 tons 16
  17. 17. of seaweed. With the removal of the particulate emissions from the mussel unit, the filtered water emerging from the seaweed unit is rendered waste-free. The Factors Influencing Nutrient Loading Feed Quality The feed coefficient and the content of phosphorus (‘P’) and nitrogen (‘N’) in the feed are two important factors to consider while assessing environmental impact of aquaculture (Ackefors, 1997). Mass balance models have shown that the discharge of nutrients and organic materials have decreased over the past two decades owing to reduction in feed conversion ratio and content of nitrogen and phosphorous in commercial salmon feed. While the feed coefficient has decreased from 2.3 to less than 1.3, the nitrogen content in the feed has decreased from 7.8% to 6.8% and that of phosphorous from 1.7% to 1.1% (Ackefors and Enell, 1990). This has resulted in lowering of discharge of nutrient per tine of produced fish. In case of nitrogen it has decreased from 129 kg to 53 kg and for phosphorus from 31 kg to 9.5 kg (Ackefors, 1997). In recent days FCR as low as 0.85 has been reported. Thus feed quality is an important factor in lowering of environmental impact of marine cage fish farming. In the present study, three different feeds have been selected for assessment of nutrient loading of the chosen technologies. In the traditional Farming System use of conventional feed with FCR value of 1.5 (‘N’= 8%; ‘P’ = 1%) has been considered. Though present day feed are much lower in ‘N’ & ‘P’ content however the assessment of ‘Area Capacity’ under ‘LENKA’ is based on this kind of feed and hence for the shake of comparison it was necessary to include this as control. The improved feed with FCR value of 1.0 (‘N’= 7.5%; ‘P’ = 0.9%) has been considered for the remaining technologies excepting one in which HND diet has been considered. FCR for the HND diet is taken as 0.83 (‘N’= 7.2%; ‘P’ = 0.9%). Thus it would be possible to compare the least efficient feed with quality feed and the nutrient dense feed. The quality feed has also been considered as the basis for mass balance modeling of the two technologies concerning i.waste recovery (Lift-up) and ii. nutrient recycling (Integrated farming). Feeding Feeding is one of the most important and expensive jobs in salmon farming. The main aim of the farmer is to achieve maximum growth from the food that is fed. No food has to be wasted as this can have a detrimental effect not only on the profitability of the farm, but also on the seabed beneath the cages. In modern day salmon farming there are three methods of administering the food to the fish. These are: 1. Feeding till Satiation A. Hand feeding. Following this method feed release is triggered by fish behavior and hence feeding is to satiation level. In this kind of feeding practice, the operative would be feeding the fishes manually by broadcasting the feed while moving from cage to cage. The farmer determines how much food is to be fed to a pen by working out the biomass of the fish within the cage. A certain percentage of this biomass is then fed to the fish daily. This percentage figure varies throughout the year and is dependant upon fish size, seawater temperature and the stock type as well as the experience of the operative in feeding the fishes. For Semi-intensive cage farming, hand feeding may be the best method since it is possible to assess fish appetite and adjust feeding rates however it may 17
  18. 18. result in overfeeding since the end point in this method is usually the point where fish stop eating. However the down side of this mode of feeding is higher labor cost and its application on large- scale commercial application. B. Demand Feeding It is a mechanical form of feeding based on the feeding behavior of the fish. Demand feeders typically consist of a feed hopper fitted with a plate that is connected to the pendulum rod that projects down into the water. When the pendulum is touched, the plate moves thereby releasing small quantities of feed. The fish can feed whenever it wants but the method could be wasteful in sea condition where, the pendulum could be stimulated by wave actions. It is more commonly used in the land-based than water-based systems (Beveridge 1996). 2. Automatic Feeding Automatic feeders depends on a feeding program pre-set by the farmer indicating ration and frequency of delivery. The farmer determines how much food is to be fed to a pen by working out the biomass of the fish within the cage. A certain percentage of this biomass is then fed to the fish daily. This percentage figure varies throughout the year and is dependant upon fish size, seawater temperature and the stock type. Dry pellet automatic feeders typically consists of a plastic feed hopper mounted on a triggering device that releases a certain quantity of feed when triggered. These are operated either by batteries or by compressed air / pressurized water (Beveridge 1986). Electrical The electrically operated systems are operated either using centralized power supply with common control unit or using individual power source and control device for independent operating of each unit. The control unit sends the required electrical impulse determining the number and duration of feeding. The operation of the feeders during daytime is ensured using a photocell. A number of cages adopting the centralized feeding can fed by a 12V battery and a control unit connected through cabling along walkways and cage superstructure. Feeding is synchronized in all the cages using the timing device. Compressed air / pressurized water system Cannon feeding is based on either compressed air or pressurized water system. Compressed air is less popular at cage sites. The compressor pressurizes an air chamber, from which bursts of air is released and fed via high-pressure pipeline connecting the feeders on the cages. The feeders consist of a hopper from which pellets fall into a delivery pipe connected to the compressed air line. When air is released into the delivery pipe pellets are blown into the cages. Compressed air feeders can operate from boat or from shore based facility (when the cages are linked by catwalk to the shore based facilities). Pressurized water systems are also used to deliver food from a centralized unit via pipeline to individual cages (Fig.4). While automatic feeding system is less labor intensive than hand feeding, it is found to be wasteful from feed utilization point of view. Thus it may result in higher feed conversion, feed cost and nutrient loading (Beveridge, 1996) 18
  19. 19. 3. Computer controlled strict feeding Regime These are relatively new adaptive feeding systems and are responsive to changes in the environment and hence an improvement over the automatic feeding system relying heavily on pre-set feeding program. These systems consist of a hydroacoustic or video sensor attached to the bottom of the cage net which is linked to a computer (Juell 1991, Juell et. al.1993; Bjordal et. al. 1993; Blyth 1992). A feeding program is preset so that a certain amount of food is fed in a certain amount of meals. If the fish are being overfed then the sensor picks up the uneaten food reaching the bottom of the pen and sends the information back to the computer, which in turn reduces the amount of food fed. Conversely the computer will increase feed input until feed pellets are detected at the bottom of the pen. Using these systems feed wastage can be reduced to 4% level and greatly improves FCR (Baird et al. 1996). Some of the most effective types of feeding systems are the ones manufactured by Aquasmart and AKVA. Three computer aided feeding systems based on hand feeding, cannon feeding and adaptive fish feeding techniques developed by Aquasmart is discussed here. i. Aquasmart PS1 Feed Monitoring System The features of PS1 Feed Monitoring System (Fig.5) are as under: • PS1 can be used with hand feeding, feed cannons, or centralized feeding systems • an underwater sensor which detects pellet sizes from 2mm to 16mm • temperature tolerance from -20 to +50 degrees Celsius • internal 12V DC battery with 100 to 240V AC recharge • radio communication • Windows-based software • and can be integrated with all centralized feeders ii. Aquasmart PS2 Feeding Control System for Feed Cannons The PS2 software can also be linked to feed cannons to record feeding rate during the meal. As the feed operator feeds the fish, the PS2 unit (Fig.6) sends information gathered by the sensor via telemetry to the computer. From here the operator can adjust the feed in relation to the appetite of the fish. If the feeding rate is too high an alarm sounds to warn the operator. iii. Aquasmart AQ1 Adaptive Fish Feeding System The AQ1 Adaptive Feeding System controls automatic feeders by accurately matching feed delivery to fish appetite. The AQ1 advanced sensor, communications system and software means an entire farm can be monitored and controlled from a centrally located PC (Fig. 7). This advanced feed optimization system features: • an underwater sensor which detects pellet sizes from 2mm to 16mm • temperature tolerance from -20 to +50 degrees Celsius • radio communication • Windows-based software • creating a complete management record of feeding Using the feeding systems based on feeding behaviour of the fish that reflects its satiation level, we may be relying on the hypothalamus control of the fish. This physiological control is stimulated by the stretch receptors in the fore-end of the gut and possibly by the blood sugar 19
  20. 20. level. Such natural physiological controls have evolved to deal with the natural food encountered in the wild. However, the nutrient content of the artificial feed being of much higher order, the supply of nutrient may be much higher than required resulting in poor FCR (Beveridge 1996). The hand feeding and the use of feed cannon are based on the above concept accounting for greater feed waste estimated to be 20% of total feed supply. The automatic feeding control systems used in conjunction with the above feeding systems is likely to have a check on the total food supply through its pre-set computer controlled feeding program as well as its monitoring system scanning the cage volume for detection of unutilised feed particles. This enables minimising feed loss to the extent of 4% of total nutrient supply. Mechanical Waste Recovery Approximately 25% of nitrogen and 75% of phosphorus wastes from open fish cage systems appear in particulate form (Hall et.al 1990; Gowen et al 1988 and Ackefors et al 1990). Mass balance models for organic carbon indicates that 7 to 66% of it is sedimented under the cages (Ackefors, 1997). Several mechanical devices have been designed to collect this particulate fraction of the wastes generated from the cage sites, which include i. Viking fish model by the Swedish company (Viking fish AB), ii. the Refa lift-up pellet sampler by a Norwegian company and iii. the Lift-up Kombi waste feed and dead fish collector (Enell et al 1984; Braathen 1992; and Ackefors, 1997). The Lift-up Kombi system is provided with a fine meshed funnel shaped net cloth, which is provided under the cage to which a tube is attached at the bottom (Fig.8). To this is attached the compressed air pipe, providing the air lift suction. Dead fish, excess feed and and large faecal particles are trapped by the lower fine-meshed net and led to the bottom of the net where a hose is connected. The waste food is collected by lifting the water from the bottom of the cage using the water lift and passed through the filtration unit that retains the particulate matter. The sludge can be used as manure (Ackefors, 1997). The Lift-up Kombi system is known to collect upto 100% surplus feed, sized 6 mm and larger and nearly 70% of 4 mm particles (Ervik et al, 1994). It is stated that “ The surplus feed collector can also reduce the general impact of fish farms on their recipients. This is most important for marginal recipients, since the life span of these locations are increased significantly. The negative environmental feedback on fishfarm in such environment will be diminished, - instead of resulting in poor health conditions and high needs of antibacterials. The higher cost of the equipment are shown to be balanced by the benefits of automatic dead fish collection, increased growth, reduced feed conversion rates and lower mortality of the fish.” Recovery of waste using Lift-up system can be based on the following assumptions. • Approximately 25% of nitrogen wastes from open fish cage systems appear in particulate form • Approximately 75% of phosphorus wastes from open fish cage systems appear in particulate form • Approximately 80% of the particulate matter emitted from the cages are collected by the Lift-up systems Using the data on nutrient load derived from mass balance equation and the above information, the recovery of nutrients can be calculated using the following expression wherein, ‘R’ is 20
  21. 21. recovery of nutrient; ‘P’ is % particulate form, ‘r’ is % recovery and ‘NL’ is nutrient load from the system. R = NL x P/100 x r/100 The recovery of wastes using the Lift-up system would depend on the nutrient content of the feed itself. In the present study improved feed with FCR of 1.0 has been considered since this form the basis of present day farming practice. Nutrient Recycling (Biological Waste Recovery) The basic pre-requisite for sustainable salmon farming would be use of clean technology based on principles of minimum nutrient / waste loading on the surrounding aquatic environment. Since production of organic wastes can not be avoided hence a clean system would either remove it mechanically or use it up within the production system itself. The goal must be a production process where the water is used only as a carrier which leaves the production plant ‘untouched’ by the production process (Bodvin et.al. 1996). This can be achieved by employing biological process that would take care of the particulate matter and the dissolved nutrient, generated on account of uneaten feed, undigested feed and excretion. Integrating farming of mussels and seaweed with fish is known to be very effective in recycling nutrients and wastes (Figure 9). Using filter feeders such as mussel / oyster / clam for reducing particulate matter and macro-algae for removing dissolved nutrient is known to be an effective biological alternative. However, this can only be effective in an enclosed system (Shpigel et al. 1993) and results from production of salmonides, mussels and macro-algae indicate such possibilities (Bodvin et.al. 1996). In fact such floating enclosed system with 50 – 60 % lower investment cost and reduced energy expenditure has been developed and tested in full-scale for the last 8 years in Norway. A theoretical model linking the production of salmon, blue mussel and seaweed in floating enclosed unit was performed during 1992-94 to minimize eutrophication from fish farming activities. Commercial viability of such aquaculture technique is expected to enable the industry to meet the Declaration of The North Sea. The model plant is based on production data from a full scale pilot farm built in Flekkefjord (Skaar & Bodvin,1993) as described by Bodvin et.al. (1996). The standard plant with production volume of 6000 m3, consisting of 12 fish units, each with a volume of 500 m3 and pumping capacity of 5.5 m3 min-1 delivers the particulate and dissolved emissions to the next unit, which is the mussel unit. Outlet water is transferred from the salmon units to 12 enclosed units (500 m3 each) with blue mussels using airlift system. The outlet is set to 50 kg total ‘N’ and 8 kg of total ‘P’ per metric ton of salmon produced. Of this the mussel units are designed to convert 25% of particulate ‘N’ and ‘P’ emissions. The dissolved ‘N’ and ‘P’ emissions from the salmon as well as mussel units are transferred to the seaweed units. The particulate wastes from the mussel units are collected in sediment trap and removed. The stocking rate of mussel is worked out considering i. all water has to be pumped at least once and that would require a pumping capacity three times larger than the water flux and ii. the standard pumping capacity of 2-3 l h-1 for a standard market size mussel weighing 25 g. The required mussel was thus assessed to be 112.5 metric tons or 9.4 metric tons fresh weight (FW) per unit or 18 kg FW per m-3. With a monthly exchange of mussels in each unit, the total turnover is assessed to be 1350 metric tons. In this model no specific estimates for a mass balance with mussel concerning total ‘P’ are used and the same is assessed using the principles for the fish unit. Seaweed production has been modelled on the basis of total utilisation of the dissolved ‘N’ by the seaweed unit. Considering a ‘N’-content of 4% for seaweed dry weight and 20% dry matter content, a total production of 1700 metric tons fresh weight (FW) of seaweed year-1 is envisaged. This in turn is based on the assumption of 4.5 metric tons of seaweed production day-1 requiring 45 metric ton of standing stock with a daily 21
  22. 22. growth rate of 10%. With 12 production units of 1000 m3, the standing stock would amount to 3.75 kg FW m-3. Considering the ‘P’-content in seaweed ( 0.2%) and dry matter content (20%), a production of about 3000 metric tonne is envisaged (Bodvin et. Al.1996). The mass balance equations for this biological system is discussed subsequently (table 14-20). Waste Quantification There are two methods for estimating material lost to the environment i.e. 1. Direct method, involving sampling and analysis of the water column and sedimenting particulate material 2. Indirect method, using mass balance equation. In the present study, mass balance equation has been used for quantifying the waste load from the selected farming systems under consideration. Following Mass Balance Equation assessment of nutrient loading in terms of Nitrogen (‘N’), Phosphorus (‘P’) and Total Solids (TS) from salmon cage farming were made. Nutrient loss through uneaten food, faecal matter and excretion can be estimated using data on feed quality and quantity, food conversion ratio (FCR), digestibility and faecal composition. The present assessment of Nitrogen and Phosphorus flow through salmonid cages has been based on the works of Beveridge (1984), Ackefors and Enell (1990) and Holby and Hall (1991). The flow chart of nutrients from feed to fish and finally to the environment as wastes is shown in Figure 10-12. As is evident from this chart, given the information on Fish Production, Feed Conversion Ratio, Feed Waste (%) and, Feed digestibility (%) derived parameters such as Feed Supply, Feed Consumed, Fecal Production can be worked out. Further, information on nutrient content of feed, nutrient content of feces and nutrient in fish biomass would enable assessment of nutrient loading. Thus total nutrient loading (NL) could be derived using the following equation wherein ‘NS’ stands for nutrient supply in feed and ‘NR’ stands for nutrient retained in fish . NL = NS - NR Information on solid wastes by way uneaten feed and feacal production could be utilized to work out the load on account of suspended solids as under. TSS = UF + FP ‘TSS’ stands for Total Suspended Solids, ‘UF’ for Unconsumed Feed ‘FP’ stands for Fecal Production. 22
  23. 23. Results The results of the study is presented in three sections 1. Mass Balance analysis 2. Production Potential assessment and 3. Economics of production using the cage systems under reference (Table 1). Table 1. Cage Systems Under Consideration Item System1 System2 System3 System4 System5 Site type A category of A category of A category of A category of A category of Northern Northern Northern Northern Northern Norway Norway Norway Norway Norway Type of Farm Floating unit Floating unit Floating unit Floating unit Floating unit 3 3 3 3 3 Cage volume 12000m 12000m 12000m 12000m 6000m Cage type Steel cage Steel cage Steel cage Steel Cage* Closed bag** 3 3 3 3 3 Cage size 800m 800m 800m 800m 500m No. ofCage 16 16 16 16 12 No.of nets 16 16 16 16 0 Water Flow Natural flow of Natural flow of Natural flow of Natural flow of Flow on account sea water sea water sea water sea water in of Air-lift of addition to flow water from fish due to air-lift unit to mussel and to seaweed Stocking rate of 7.5 10 10 10 15 smolt/ m3 Duration of 24 24 24 24 24 rearing (months) Mortality 15 15 15 15 15 Production in MT 300 370 370 370 300 Type of Feeding Automatic Aquasmart Aquasmart Automatic Automatic system feeder adaptive adaptive feeding feeder feeder feeding system system Type of Feed Dry pelleted Improved feed HND diet Improved feed Improved feed (FCR:1.5) (FCR:1.0) (FCR:0.83) (FCR:1.0) (FCR:1.0) Feeding principle Feeding to Strict feeding Strict feeding Feeding to Feeding to satiation regime regime satiation satiation Feed Waste 20% 5% 5% 4% 10%*** Special Feature if Designed to Represents Indicates the The possibilities Biological any meet the The existing impact of further of mechanical solution to norms under farming system improvement in recovery of nutrient loading ‘LENKA’ feed quality waste feed system Processing Hired Hired Hired Hired Hired facility Packaging Hired Hired Hired Hired Hired facilities *Lift up Kombi system to meet Norwegian Govt Regulation **Refers to close bag system (Bodvin,1996), built in Flekkefjord in 1990 ***There is apparent feed wastage, which although not eaten by fish, is removed by the filter feeders System1= Traditional farming system with conventional feed (FCR: 1.5) & no feeding control System2= Farming System with improved feed (FCR: 1.0) & strict feeding regime System3= Farming System with HND feed (FCR: 0.83) & strict feeding regime System4= Farming System with Lift up feed system System5= Integrated farming involving fish, mussel & sea weed 23
  24. 24. Mass Balance Analysis i. Traditional Farming System using conventional feed and feeding mechanism (System) Following the traditional system 16 cages with cage volume of 800 m3 each have been considered of which 15 would be under production with one stand-by cage. Thus the effective production volume is estimated to be 12000 m3. Considering a stocking rate of 7.5 smolt / m3, 85% survival and an average harvest weight of 4kg salmon, the final harvest is expected to be 300 kg. The use of automatic feeder type with pre-set feeding program would ensure feeding till satiation but since it is not adapted to regulate feeding on the basis of behavioral response of the fish, considerable feed wastage)(20%) is involved in this mode of feeding. In the traditional Farming System use of conventional feed with FCR value of 1.5 (‘N’= 8%; ‘P’ = 1%) has been considered following the provisions under ‘LENKA’ system. The mass balance analysis of nitrogen, phosphorus and suspended solids have been worked out (table 2-4) Table 2. Mass Balance Equation for Nitrogen (System 1) Sl.No Items Formula Estimation . 1 Fish Production (kg) A 1000 2 Feed Conversion Ratio B 1.5 3 Feed Supply (kg) C=AxB 1500 4 Feed Wastage (%) Dw 20 5 Feed Waste (kg) D = C x Dw / 100 300 5 Feed Consumed (kg) E = C (100 – Dw)/ 100 1200 6 Feed Undigested (%) F 25 7 Fecal Production (kg) G = E x F / 100 300 8 Nitrogen Content of Feed (%) H 8 9 Nitrogen Content of Feces (%) I 4 10 Nitrogen in Feed Supply (kg) J = C x H / 100 120 11 Nitrogen in Feed Waste (kg) K = D x H / 100 24 12 Nitrogen Ingested (kg) L = E x H / 100 96 13 Nitrogen Retained in Fish @ 3% (kg) M = A x 3 /100 30 14 Total Nitrogen Excreted (kg) N=L–M 66 15 Nitrogen in Feces (kg) O = G x I / 100 12 16 Nitrogen in Catabolic Product (kg) P=N–O 54 17 Total Nitrogen Load (kg) Q=K+O+P 90 18 Recovery of Nitrogen Load if any (kg) R 0 19 Net Nitrogen Load on environment (kg) S=Q-R 90 24
  25. 25. Table 3. Mass Balance Equation for Phosphorus (System 1) Sl.No Items Formula Estimatio . n 1 Fish Production (kg) A 1000 2 Feed Conversion Ratio B 1.5 3 Feed Supply (kg) C=AxB 1500 4 Feed Wastage (%) Dw 20 5 Feed Waste (kg) D = C x Dw / 100 300 5 Feed Consumed (kg) E = C (100 – Dw)/ 100 1200 6 Feed Undigested (%) F 25 7 Fecal Production (kg) G = E x F / 100 300 8 Phosphorus Content of Feed (%) H 1 9 Phosphorus Content of Feces (%) I 1.5 10 Phosphorus in Feed Supply (kg) J = C x H / 100 15 11 Phosphorus in Feed Waste (kg) K = D x H / 100 3 12 Phosphorus Ingested (kg) L = E x H / 100 12 13 Phosphorus Retained in Fish @ 0.4 % (kg) M = A x 0.4 /100 4 14 Total Phosphorus Excreted (kg) N=L–M 8 15 Phosphorus in Feces (kg) O = G x I / 100 4.5 16 Phosphorus in Catabolic Product (kg) P=N–O 3.5 17 Total Phosphorus Load (kg) Q=K+O+P 11 18 Recovery of Phosphorus Load if any (kg) R 0 19 Net Phosphorus Load on environment (kg) S=Q-R 11 Table 4. Mass Balance Equation for Total Solids (System 1) Sl.No Items Formula Estimate . 1 Unconsumed Feed (kg) D = C x Dw / 100 300 2 Fecal Production (kg) G = E x F / 100 300 3 Total Solid Load (kg) H=D+G 600 4 Recovery of Solid Load if any (kg) R 0 5 Net Solid Load on environment (kg) S=H-R 600 Following the traditional farming system the expected nutrient load on the environment on the basis of mass balance analysis amounts to 90 kg Nitrogen, 11 kg phosphorus and 600 kg solid waste (Fig.13). ii. Improved Farming System using efficient feed and feeding mechanism (System 2) In this system improved feed with FCR value of 1.0 (‘N’= 7.5%; ‘P’ = 0.9%) has been considered. A strict feeding regime is envisaged using computer aided ‘Adaptive Feeding System’ that controls automatic feeders by accurately matching feed delivery to fish appetite. This enables minimising feed loss to the extent of 4% of total nutrient supply. In this model feed wastage to the extent of 5% has been considered. The production program is based on a cage volume of 12000 m3 that is expected to produce 370 tons of fish, stocked at the rate of 10 smolt/ m3 with 15% survival and average weight of 3.7 kg/fish. The mass balance analysis of nitrogen, phosphorus and suspended solids have been worked out (table 5-7). 25
  26. 26. Following the Improved farming system involving quality feed and adaptive feeding technique the expected nutrient load on the environment using mass balance analysis is estimated to be 45kg Nitrogen, 5 kg phosphorus and 240 kg solid waste (Fig.14). A better food conversion and reduced nutrient loss is achieved compared to system 1 on account of better feed utilization nutrient profile. Table 5. Mass Balance Equation for Nitrogen (System 2) Sl.No Items Formula Estimation 1 Fish Production (kg) A 1000 2 Feed Conversion Ratio B 1 3 Feed Supply (kg) C=AxB 1000 4 Feed Wastage (%) Dw 5 5 Feed Waste (kg) D = C x Dw / 100 50 5 Feed Consumed (kg) E = C (100 – Dw) / 100 950 6 Feed Undigested (%) F 20 7 Fecal Production (kg) G = E x F / 100 190 8 Nitrogen Content of Feed (%) H 7.5 9 Nitrogen Content of Feces (%) I 4 10 Nitrogen in Feed Supply (kg) J = C x H / 100 75 11 Nitrogen in Feed Waste (kg) K = D x H / 100 3.75 12 Nitrogen Ingested (kg) L = E x H / 100 71.25 13 Nitrogen Retained in Fish @ 3% (kg) M = A x 3 /100 30 14 Total Nitrogen Excreted (kg) N=L–M 41.25 15 Nitrogen in Feces (kg) O = G x I / 100 7.6 16 Nitrogen in Catabolic Product (kg) P=N–O 33.65 17 Total Nitrogen Load (kg) Q=K+O+P 45 18 Recovery of Nitrogen Load if any (kg) R 0 19 Net Nitrogen Load on environment (kg) S = Q - R 45 Table 6. Mass Balance Equation for Phosphorus (System 2) Sl.No Items Formula Estimatio . n 1 Fish Production (kg) A 1000 2 Feed Conversion Ratio B 1 3 Feed Supply (kg) C=AxB 1000 4 Feed Wastage (%) Dw 5 5 Feed Waste (kg) D = C x Dw / 100 50 5 Feed Consumed (kg) E = C (100 – Dw)/ 100 950 6 Feed Undigested (%) F 20 7 Fecal Production (kg) G = E x F / 100 190 8 Phosphorus Content of Feed (%) H 0.9 9 Phosphorus Content of Feces (%) I 1.5 10 Phosphorus in Feed Supply (kg) J = C x H / 100 9 11 Phosphorus in Feed Waste (kg) K = D x H / 100 0.45 12 Phosphorus Ingested (kg) L = E x H / 100 8.55 13 Phosphorus Retained in Fish @ 0.4 % (kg) M = A x 0.4 /100 4 14 Total Phosphorus Excreted (kg) N=L–M 4.55 15 Phosphorus in Feces (kg) O = G x I / 100 2.85 26
  27. 27. 16 Phosphorus in Catabolic Product (kg) P=N–O 1.7 17 Total Phosphorus Load (kg) Q=K+O+P 5 18 Recovery of Phosphorus Load if any (kg) R 0 19 Net Phosphorus Load on environment (kg) S=Q-R 5 Table 7. Mass Balance Equation for Total Solids (System 2) Sl.No Items Formula Estimation . 1 Unconsumed Feed (kg) D = C x Dw / 100 50 2 Fecal Production (kg) G = E x F / 100 190 3 Total Solid Load (kg) H=D+G 240 4 Recovery of Solid Load if any (kg) R 0 5 Net Solid Load on environment (kg) S=H-R 240 iii. Improved Farming System using HND feed and efficient feeding mechanism (System 3) In this system high energy nutrient dense diet with FCR value of 0.83 (‘N’= 7.2%; ‘P’ = 0.9%) has been considered. A strict feeding regime is envisaged using computer aided ‘Adaptive Feeding System’ as in the case of the earlier system. The production program is based on a cage volume of 12000 m3 that is expected to produce 370 tons of fish, stocked at the rate of 10 smolt/ m3 with 15% survival and average weight of 3.7 kg/fish. The mass balance analysis of nitrogen, phosphorus and suspended solids have been worked out (table 8-10). Table 8. Mass Balance Equation for Nitrogen (System 3) Sl.No Items Formula Estimation . 1 Fish Production (kg) A 1000 2 Feed Conversion Ratio B 0.83 3 Feed Supply (kg) C=AxB 830 4 Feed Wastage (%) Dw 5 5 Feed Waste (kg) D = C x Dw/ 100 41.5 5 Feed Consumed (kg) E = C (100 – Dw)/ 788.5 100 6 Feed Undigested (%) F 18 7 Fecal Production (kg) G = E x F / 100 142 8 Nitrogen Content of Feed (%) H 7.2 9 Nitrogen Content of Feces (%) I 4 10 Nitrogen in Feed Supply (kg) J = C x H / 100 59.76 11 Nitrogen in Feed Waste (kg) K = D x H / 100 2.99 12 Nitrogen Ingested (kg) L = E x H / 100 56.77 13 Nitrogen Retained in Fish @ 3% (kg) M = A x 3 /100 30 14 Total Nitrogen Excreted (kg) N=L–M 26.77 15 Nitrogen in Feces (kg) O = G x I / 100 5.68 16 Nitrogen in Catabolic Product (kg) P=N–O 21.09 17 Total Nitrogen Load (kg) Q=K+O+P 29.76 18 Recovery of Nitrogen Load if any (kg) R 0 19 Net Nitrogen Load on environment (kg) S = Q – R 29.76 27
  28. 28. Table 9. Mass Balance Equation for Phosphorus (System 3) Sl.No Items Formula Estimation . 1 Fish Production (kg) A 1000 2 Feed Conversion Ratio B 0.83 3 Feed Supply (kg) C=AxB 830 4 Feed Wastage (%) Dw 5 5 Feed Waste (kg) D = C x Dw/ 100 41.5 5 Feed Consumed (kg) E = C (100 – Dw)/100 788.5 6 Feed Undigested (%) F 18 7 Fecal Production (kg) G = E x F / 100 142 8 Phosphorus Content of Feed (%) H 0.9 9 Phosphorus Content of Feces (%) I 1.5 10 Phosphorus in Feed Supply (kg) J = C x H / 100 7.47 11 Phosphorus in Feed Waste (kg) K = D x H / 100 0.37 12 Phosphorus Ingested (kg) L = E x H / 100 7.1 13 Phosphorus Retained in Fish @ 0.4 % (kg) M = A x 0.4 /100 4 14 Total Phosphorus Excreted (kg) N=L–M 3.1 15 Phosphorus in Feces (kg) O = G x I / 100 2.13 16 Phosphorus in Catabolic Product (kg) P=N–O 0.97 17 Total Phosphorus Load (kg) Q=K+O+P 3.47 18 Recovery of Phosphorus Load if any (kg) R 0 19 Net Phosphorus Load on environment (kg) S=Q-R 3.47 Table 10. Mass Balance Equation for Total Solids (System 3) Sl.No Items Formula Estimate . 1 Unconsumed Feed (kg) D = C x d / 100 41.5 2 Fecal Production (kg) G = E x F / 100 142 3 Total Solid Load (kg) H=D+G 183.5 4 Recovery of Solid Load if any (kg) R 0 5 Net Solid Load on environment (kg) S=H–R 183.5 Following this farming system involving high nutrient dense (HND) diet and adaptive feeding technique the expected nutrient load on the environment using mass balance analysis is estimated to be 29.76 kg Nitrogen, 3.47 kg phosphorus and 184 kg solid waste (Fig.15). A better food conversion and reduced nutrient loss is achieved compared to system 1&2. The low-protein, high-fat composition of these feeds with protein sparing effect help in reducing protein catabolism and consequent stimulation of anabolic process thus improving FCR while reducing excretion of nitrogenous and phosphorus wastes. iv. Farming System using efficient feed and Lift-up feed collector (System 4) The Lift-up Kombi system removes dead fish, excess feed and and large faecal particles. The Lift-up system is known to collect up to 100% surplus feed, sized 6 mm and larger and nearly 70% of 4 mm particles (Ervik et al, 1994). The present assessment is based on 80% recovery of waste feed and particulate ‘N’ and ‘P’ excretion. 28
  29. 29. The production program is based on a cage volume of 12000 m3 that is expected to produce 370 tons of fish, stocked at the rate of 10 smolt/ m3 with 15% survival and average weight of 3.7 kg/fish. The mass balance analysis of nitrogen, phosphorus and total solids have been worked out (table 11-13). Table 11. Mass Balance Equation for Nitrogen (Lift up System) Sl.No Items Formula Estimation . 1 Fish Production (kg) A 1000 2 Feed Conversion Ratio B 1 3 Feed Supply (kg) C=AxB 1000 4 Apparent Feed Wastage (%) Da 20 5 Recovery of feed @ 80 % Rf = C x Da/100 x 160 80/100 6 Net feed waste (kg) D = (C x Da) – Rf 40 7 Net feed wastage (%) Dw = (D / C) x 100 4 8 Feed Consumed (kg) E = C (100 – Dw) / 100 960 9 Feed Undigested (%) F 20 10 Fecal Production (kg) G = E x F / 100 192 11 Nitrogen Content of Feed (%) H 7.5 12 Nitrogen Content of Feces (%) I 4 13 Nitrogen in Feed Supply (kg) J = C x H / 100 75 14 Nitrogen in Feed Waste (kg) K = D x H / 100 3 15 Nitrogen Ingested (kg) L = E x H / 100 72 16 Nitrogen Retained in Fish @ 3% B.W. M = A x 3 /100 30 17 Total Nitrogen Excreted (kg) N=L–M 42 18 Nitrogen in Feces (kg) O = G x I / 100 7.68 19 Nitrogen in Catabolic Product (kg) P=N–O 34.32 20 Total Nitrogen Load (kg) Q=K+O+P 45 21 Particulate Nitrogen Load (@ 25 %) (kg) Pn = Q x 25 / 100 11.25 22 Recovery of Particulate ‘N’ (@ 80%) Rn = Pn x 80 / 100 9 (kg) 23 Net particulate ‘N’ Load on environment Sn = Pn – Rn 2.25 (kg) 24 Dissolved Nitrogen Load (@ 75 % (kg) Dn = Q x 75 / 100 33.75 25 Total ‘N’ Load on environment (kg) Tn = Sn + Dn 36 Following lift-up system involving reuse of waste feed and recovery of particulate excretory matter, the expected nutrient load on the environment using mass balance analysis is estimated to be 36 kg Nitrogen, 2 kg phosphorus and 43 kg solid waste (Fig.16). Thus a reduction in nutrient loss is achieved when compared to system 1&2. The trend is somewhat different when compared to system 3 wherein, the emission of nitrogen is observed to be lower in system 3 but the emission of phosphorus and suspended solid is lower in system 4. This could be attributed to low generation of nitrogenous wastes in system 3 on account of protein sparing in HND diets and its low recovery in system 4 owing to lower particulate fraction (25%) compared to phosphorus and suspended solids. While the generation of phosphorus waste is actually higher in system 4, the lower loading is on account of substantial recovery of phosphorus in which particulate fraction is as high as 75%. 29
  30. 30. Table 12. Mass Balance Equation for Phosphorus (Lift up System) Sl.No Items Formula Estimation . 1 Fish Production (kg) A 1000 2 Feed Conversion Ratio B 1 3 Feed Supply (kg) C=AxB 1000 4 Apparent Feed Wastage (%) Da 20 5 Recovery of feed @ 80 % Rf = C x Da/100 x 160 80/100 6 Net feed waste (kg) D = (C x Da) - Rf 40 7 Net feed wastage (%) Dw = (D / C) x 100 4 8 Feed Consumed (kg) E = C (100 – Dw) / 100 960 9 Feed Undigested (%) F 20 10 Fecal Production (kg) G = E x F / 100 192 11 Phosphorus Content of Feed (%) H 0.9 12 Phosphorus Content of Feces (%) I 1.5 13 Phosphorus in Feed Supply (kg) J = C x H / 100 9 14 Phosphorus in Feed Waste (kg) K = D x H / 100 0.36 15 Phosphorus Ingested (kg) L = E x H / 100 8.64 16 Phosphorus Retained in Fish @ 3% B.W. M = A x 3 /100 4 17 Total Phosphorus Excreted (kg) N=L–M 4.64 18 Phosphorus in Feces (kg) O = G x I / 100 2.88 19 Phosphorus in Catabolic Product (kg) P=N–O 1.76 20 Total Phosphorus Load (kg) Q=K+O+P 5 21 Particulate ‘P’ Load @ 75 % (kg) Pp = Q x 75 / 100 3.75 22 Recovery of Particulate ‘P’ (@ 80%) (kg) Rp = Pp x 80 / 100 3 23 Net particulate ‘P’ Load on Environment Sp = Pp – Rp 0.75 (kg) 24 Dissolved Phosphorus Load (@ 75 % Dp = Q x 25 / 100 1.25 (kg) 25 Total ‘P’ Load on environment (kg) Tp = Sp + Dp 2 Table 13. Mass Balance Equation for Total Solids (Lift-up System) Sl.No Items Formula Estimation . 1 Net feed waste (kg) D = (C x Da) - Rf 40 2 Net particulate ‘P’ Load on Env. (kg) Sp = Pp – Rp 0.75 3 Net particulate ‘N’ Load on Sn = Pn – Rn 2.25 environment (kg) 4 Net Solid Load on environment (kg) S = D + Sp + Sn 43 V. Closed Bag Integrated Farming System (System 5) The model plant is based on production data from a full scale pilot farm built in Flekkefjord (Skaar & Bodvin, 1993) as described by Bodvin et.al. (1996). The standard plant comprising 1. fish production section of 6000 m3 (12 fish units, each with a volume of 500 m3) linked to 2. mussel production section of 6000 m3 (12 mussel units, each with a volume of 500 m3), which in turn is linked to 3. seaweed section of 12000 m3 (12 seaweed units, each with a volume of 1000 m3). The fish unit with stocking rate of 15 smolt m3 and 85% survival is estimated to produce 30
  31. 31. 300 tons of fish. In order to trap the particulate emissions from the fish unit 1350 tons (fresh weight) of mussel is required. The dissolved outflow from the fish unit as well as the mussel unit is estimated to support 3000 tons of seaweed. With the removal of the particulate emissions from the mussel unit, the filtered water emerging from the seaweed unit is rendered waste-free. The mass balance analysis of nitrogen, phosphorus and solids have been worked out (table 14-16). Table 14. Mass Balance Equation for Nitrogen ( Biological Waste Recovery) Fish Unit Sl.No Items Formula used Estimation . 1 Fish Production (kg) A 1000 2 Feed Conversion Ratio B 1 3 Feed Supply (kg) C=AxB 1000 4 Feed Wastage (%) D 10* 5 Feed Consumed (kg) E = C (100 – D)/100 900 6 Feed Undigested (%) F 20 7 Fecal Production (kg) G = E x F / 100 180 8 Nitrogen Content of Feed (%) H 7.5 9 Nitrogen Content of Feces (%) I 4 10 Nitrogen in Feed Supply (kg) J = C x H / 100 75 11 Nitrogen in Feed Waste (kg) K = C x D/100 x H/ 100 7.5 12 Nitrogen Ingested (kg) L = E x H / 100 67.5 13 Nitrogen Retained in Fish @ 3% B.W. (kg) M = A x 3 /100 30 14 Total Nitrogen Excreted (kg) N=L–M 37.5 15 Nitrogen in Feces (kg) O = G x I / 100 7.2 16 Nitrogen in Catabolic Product (kg) P=N–O 30.3 17 Total Nitrogen Load (kg) Q=K+O+P 45 18 Recovery of Nitrogen Load if any (kg) R 45 19 Net Nitrogen Load from fish unit on S = Q - R 0 environment (kg) Recovery of Nitrogen Load 20 Nitrogen Load - Particulate @13.5% (kg) Np1 = Q x 13.5 / 100 6 Supply to Mussel Unit 21 Nitrogen Load - Dissolved @86.5% (kg) Nd 1= Q x 86.5 / 100 39 Supply to Seaweed unit *Feed wastage @ 10% has been considered taking into account 1. lack of strict feeding regime and 2. greater feed availability considering closed environment of the unit 31
  32. 32. Mussel Unit Sl.No Items Formula used Estimation . 1 Nitrogen Load From Fish Unit - Np1 6** Particulate (kg) 2 Nitrogen Transferred to Mussel biomass Nm = Np1 x 25 / 100 1.5 @25% of supply (kg) 3 Nitrogen in Feces @ 25% of supply Nf = Np1 x 25 / 100 1.5 4 Dissolved Nitrogen load - @50% (kg) Nd2 = Np1 x 50 / 100 3 5 Total Nitrogen load from Mussel Unit (kg) Tn = Nf + Nd2 4.5 6 Recovery of Nitrogen load from feces (kg) Using sediment trap 1.5 7 Recovery of Dissolved Nitrogen load (kg) Supply to Seaweed Unit 3 8 Total recovery of Nitrogen load from Item 6 + 7 4.5 Mussel Unit (kg) 9 Net Nitrogen Load from Mussel Unit on Item (5 – 8) 0 environment (kg) Sea Weed Unit Sl.No Items Formula used Estimation . 1 Dissolve 'N' Load of Fish Unit (kg) Nd1 39 2 Dissolve 'N' Load of Mussel Unit (kg) Nd2 3 3 Total Dissolved 'N' Load on Sea weed (kg) Nd = Nd1 + Nd2 42 4 Dissolve 'N' utilized by Seaweed Unit (kg) 42*** 5 Net Nitrogen Load from Sea Weed Unit Item ( 3 – 4 ) 0 on environment (kg) **Nitrogen Assimilation by Mussel unit 1. Particulate ‘N’ supply per ton fish = 6 kg 2. Total particulate ‘N’ supply from 300 ton fish = 1800 kg 3. Quantity of biomass that can be generated, considering 25% retention =.450 kg 4. Mussel’s pumping capacity with flow rate of 60 m3 min-1 @ 3times flow = 180 m3 min-1 5. Requirement of mussel considering flow rate of 2.5 l h-1 (25 gm size)= 4.32 m(approx. 4.5m) 6. Considering fresh weight (FW) of 25 gm, the requirement of mussel = 112.5 metric tons 7. With an exchange of mussel @ 112.5 mt. once a month, total annual requirement = 1350 mt. 8. Actual biomass produced on the basis of filtration requirement being higher than the nutrient etention, the total particulate ‘N’ load is expected to be bio-utilized ***Nitrogen Assimilation by Seaweed unit 1. Dissolved ‘N’ supply per ton of fish integrated with mussel = 42 kg 2. Total dissolved ‘N’ load from the entire unit / year = 12600 kg 3. Requirement of seaweed production (DW) in order to bind the dissolved ‘N’ load @ 4%(DW) = 315 mt 4. Fresh Weight of required seaweed production / year, considering 20% dry matter = 1575 mt 5. The per day production requirement of seaweed = 4.32 mt 6. The requirement of standing biomass @ 10% growth day-1= 43.2 mt 7. Considering 12 production units of 1000m3 capacity each, the standing stock m-3 = 3.6 kg 32

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