Env Plg Marine Cage Fish

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

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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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Table 3. Mass Balance Equation for Phosphorus (System 1)
Sl.No Items Formula Estimatio
. n
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
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

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.

2 Feed Conversion Ratio B 1
5 Feed Consumed (kg) E = C (100 – Dw) / 100 950
8 Nitrogen Content of Feed (%) H 7.5
11 Nitrogen in Feed Waste (kg) K = D x H / 100 3.75
12 Nitrogen Ingested (kg) L = E x H / 100 71.25
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
19 Net Nitrogen Load on environment (kg) S = Q - R 45

Sl.No Items Formula Estimatio
. n
8 Phosphorus Content of Feed (%) H 0.9
11 Phosphorus in Feed Waste (kg) K = D x H / 100 0.45
12 Phosphorus Ingested (kg) L = E x H / 100 8.55
14 Total Phosphorus Excreted (kg) N=L–M 4.55
26

19 Net Phosphorus Load on environment (kg) S=Q-R 5

.
1 Unconsumed Feed (kg) D = C x Dw / 100 50
3 Total Solid Load (kg) H=D+G 240
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.
kg/fish. The mass balance analysis of nitrogen, phosphorus and suspended solids have been
worked out (table 8-10).

.
5 Feed Waste (kg) D = C x Dw/ 100 41.5
5 Feed Consumed (kg) E = C (100 – Dw)/ 788.5
100
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
17 Total Nitrogen Load (kg) Q=K+O+P 29.76
19 Net Nitrogen Load on environment (kg) S = Q – R 29.76

27

.
5 Feed Waste (kg) D = C x Dw/ 100 41.5
5 Feed Consumed (kg) E = C (100 – Dw)/100 788.5
10 Phosphorus in Feed Supply (kg) J = C x H / 100 7.47
17 Total Phosphorus Load (kg) Q=K+O+P 3.47
19 Net Phosphorus Load on environment (kg) S=Q-R 3.47

Sl.No Items Formula Estimate
.
1 Unconsumed Feed (kg) D = C x d / 100 41.5
3 Total Solid Load (kg) H=D+G 183.5
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

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)
.
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
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
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

Table 12. Mass Balance Equation for Phosphorus (Lift up System)
.
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
16 Phosphorus Retained in Fish @ 3% B.W. M = A x 3 /100 4
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)
.
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

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
.
4 Feed Wastage (%) D 10*
5 Feed Consumed (kg) E = C (100 – D)/100 900
11 Nitrogen in Feed Waste (kg) K = C x D/100 x H/ 100 7.5
13 Nitrogen Retained in Fish @ 3% B.W. (kg) M = A x 3 /100 30
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

Mussel Unit
.
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
.
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

Env Plg Marine Cage Fish

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