Cage Aquaculture, Third Edition

375 Pages·2004·3.18 MB·English

Cage Aquaculture
Third Edition
Malcolm C. M. Beveridge
Cage Aquaculture
© 1996, 2004 by Blackwell Publishing Ltd
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First edition published 1987
Second edition published 1996 by Fishing News Books, a division of Blackwell Science
Third edition published 2004 by Blackwell Publishing
Library of Congress Cataloging-in-Publication Data
Beveridge, Malcolm C. M.
Cage aquaculture/Malcolm C. M. Beveridge. – 3rd ed.
p. cm.
Includes bibliographical references (p. ).
ISBN 1-4051-0842-8 (pbk. : alk. paper)
1. Cage aquaculture. 2. Cage aquaculture – Environmental aspects. I. Title.
SH137.3.B48 2004
639.8 – dc22
2004000842
ISBN 1-4051-0842-8
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Contents
Preface vii
Acknowledgements vii
1 Cage Aquaculture – Origins and Principles 1
1.1 Principles of aquaculture 2
1.2 Rearing facilities 4
1.3 The origins of cage culture 6
2 Cage Aquaculture – An Overview 9
2.1 Diversity of cage types 9
2.2 Cages and cage aquaculture 14
2.3 Cage culture and aquaculture 22
2.4 Advantages and disadvantages of cage culture 24
3 Cage Design and Construction 32
3.1 Shape, size and materials 33
3.2 Traditional designs 37
3.3 Modern designs 40
Appendix 3.1 Current force on a single panel of a net cage
(from Løland 1993a) 107
Appendix 3.2 Example of cage flotation computation 109
Appendix 3.3 Calculation of the buoyancy of a 3 ¥ 3 ¥ 3m
bamboo cage (see section 3.3.2) 110
4 Site Selection 111
4.1 Environmental criteria for farmed aquatic species 111
4.2 Environmental criteria for cages 134
4.3 Site facilities and management 151
4.4 Concluding remarks 155
5 Environmental Impacts and Environmental Capacity 159
5.1 Resource consumption 159
5.2 The cage aquaculture process 163
5.3 Wastes 164
5.4 Modelling environmental capacity 183
v
vi Contents
Appendix 5.1 Example of intensive cage rainbow trout production
assessment for a temperate natural lake (see section
5.4.1) (modified from Beveridge 1984a) 198
Appendix 5.2 Example of extensive cage tilapia production for a
tropical reservoir (see section 5.4.1) (modified from
Beveridge 1984a) 199
Appendix 5.3 Example of semi-intensive cage tilapia production
assessment for a tropical lake (see section 5.4.1)
(modified from Beveridge 1984a) 199
6 Management 201
6.1 Transport and stocking 201
6.2 Feeds and feeding 209
6.3 Routine management 226
7 Problems 240
7.1 Currents 241
7.2 Disease 243
7.3 Drifting objects 250
7.4 Fouling 251
7.5 Oxygen 256
7.6 Security 265
7.7 Predators and scavengers 265
7.8 Wastes 275
7.9 Weather and climate 281
Appendix 7.1 Example of calculation for a aeration system design
for a freshwater rainbow trout cage, assuming airlift
pumps are employed 307
References 308
Index 361
Preface
Since the first edition of this book seventeen years ago, aquaculture has con-
solidated its position as an important means of producing food and a contribu-
tor to global food security. Cage aquaculture too has continued to expand. While
undoubtedly there is more caged fish production in fresh waters than in marine
environments, there has been much expansion in the intensive rearing of species
such as Atlantic salmon – a fifteen-fold increase in as many years – sea bass and
sea bream in coastal environments.
The third edition tries to maintain the original aim of producing a synthesis
of information on cages and cage aquaculture practices. The past ten years have
seen tremendous advances in the body of knowledge pertaining to aquaculture.
For example, studies of the behaviour of farmed aquatic animals have resulted
in improved welfare, growth and survival of stock and reductions in wastes.
However, if cage aquaculture is to continue to develop and contribute to global
food supplies, its reliance on environmental goods and services must be fully
considered. Context is important and judgements on resource use, economic
and social impacts must be made in the widest possible context, including
alternative means of food production. With expansion and intensification of
production methods, integration with other users of coastal and freshwater
environments, too long ignored, is now crucial.
As in previous editions, this book is intended as a source or reference book
rather than as a practical manual and the new edition contains many new
references. Its format is little altered, although the balance between sections has
been changed to accommodate new information and to reflect redundancy in
certain practices.
I have included little information on cage or equipment suppliers but refer
readers to the internet, to trade papers such as Fish Farmer, Fish Farming
International, Northern Aquaculture, and to the trade directories published by
the European Aquaculture Society and Aquaculture Magazine.
ACKNOWLEDGEMENTS
While I have recently moved on to pastures new, this book is very much the product
of my long association with the Institute of Aquaculture, University of Stirling – I
could not have written it if I had not been a member of staff there for more than
twenty years. I am particularly indebted to my former colleagues, especially
Donald Baird, Paul Bulcock, Arturo Chacon Torres, Yrong Song Chen, Roy
Clarke, Sylvain Huchette, Kim Jauncey, Sunil Kadri, Liam Kelly, Dave Little,
James Muir, Kenny McAndrew, Anne Nimmo, Oscar Pérez, Mike Phillips, Lindsay
Ross, Fernando Starling, Alan Stewart, Billy Struthers, Trevor Telfer and Md.
Abdul Wahab.
vii
viii Preface
I thank the organizations that have supported me over the years in my work
on cages, especially the Overseas Development Administration of the UK
Government (now the Department for International Development, DFID) and
the Highlands and Islands Development Board (now Highlands and Islands
Enterprise, HIE). The Food and Agriculture Organization of the United Nations
awarded me an Andre Mayer Fellowship to work at the College of Fisheries,
University of the Philippines, and the short period spent in that wonderful
country greatly influenced my views of aquatic environments, their conservation
and management.
Many people have been involved in the evolution and development of this
edition of the book and I would particularly like to thank the individuals and
organizations who provided information and photographs: Mr Ismael Awang
Kechik, Mr Håkan Berg, Dr Asbjorn Bergheim, Mr Alastair Blair, Dr Peter Blyth,
Dr Giles Boeuf, Dr Alastair Bullock, Dr Andre Coche, Mr Richard Collins, Dr
James Deverill, Dr David Edwards, Dr Magnus Enell, Fusion Marine (One-steel
and Mr Coulsen), Dr John Hambrey, Dr John Hargreaves, Dr Steve Hodson,
Professor John Huguenin, Dr Kim Jauncey, Professor J. Katoh, Professor Nils
Kautsky, Dr Liam Kelly, W&J Knox, Dr M. Kuwa, Dr Geir Løland, Mr Ian
Macrae, Mr Ken McAndrew, Professor James Muir, Dr Mike Phillips, Dr Roger
Pullin, Professor Ron Roberts, Dr Derek Robertson, Sadco-shelf, Professor T.
Sano, Professor Christina Sommerville, Dr Alan Stewart, Stirling Environmental
Services, Dr Trevor Telfer, Dr Max Troell, Mr Barney Whelan and Dr F
Willumsen. Many people also helped with the production of illustrations and
graphs: Graham Brown, Rachel Delaney, Brian Howie, Liam Kelly and Denise
Macrae at the University of Stirling and David Hay at Fisheries Research Ser-
vices, Scotland. To all, I owe a debt of thanks.
Last, but not least, I would like to thank my family – Maggie, Sandy and
Charlotte – for their patience and constant support.
Cage Aquaculture, Third Edition
Malcolm C. M. Beveridge
Copyright © 1996, 2004 by Blackwell Publishing Ltd
Chapter 1
Cage Aquaculture – Origins
and Principles
Aquaculture is the aquatic counterpart of agriculture and its origins extend back
some 4000 years (Beveridge & Little 2002). However, unlike agriculture, which
has been the most important way of obtaining food on land for several thousand
years, aquaculture has until recently contributed little in real terms to world fish
or shellfish production. Instead of evolving towards cultivation, hunter–gatherer
methods of procuring food from the aquatic environment developed along a dif-
ferent path: by improvements in finding prey and by increases in killing power.
There are several reasons why agriculture and aquaculture did not develop in
the same way. First, food in the lakes and seas has, until recently, been abundant.
Increases in fishing pressure and development of fisheries technology were suffi-
cient to meet growing demands and there was, therefore, little need to learn to
farm. Moreover, the aquatic environment was hostile and something to be feared.
It must have seemed impossible that a structure that could hold fish securely and
withstand the forces of the tides and currents, waves and storms, could be built in
the sea. There were other technical problems, too, to overcome. While the breed-
ing and husbandry of animals and the harvesting and planting of seeds was readily
achieved on land, it has proved difficult to breed many aquatic species, to hatch
the eggs and to successfully rear the offspring. The problems in part stemmed from
the fact that people were dealing with organisms that were very different from
themselves and with an environment about which they were largely ignorant. It
was not until the rise of the biological sciences in the 19th century that the mys-
teries surrounding the physiology and reproduction of aquatic animals, and the
role the environment played in controlling these processes, began to be solved.
World demand for fish, both as a source of food for human consumption and
for reduction to fishmeal, has grown at a steady pace since the end of World
War II. Until recently demands were met by the expansion of capture fisheries.
Growth was around 5% during the 1950s and 1960s, increasing to 8%
during the 1980s, and to 10% per annum during the past decade, production
peaking at 95 million tonnes in 2000 (FAO 2003) (Fig. 1.1). However, when
production from China is excluded, the supplies of fish for human food have
changed little since the mid-1980s. There is a dwindling number of conventional
stocks that can sustain further increases in exploitation and the situation has
been exacerbated by steep increases in fuel oil prices, the development of
economic exclusion zones (EEZs), the over-capitalization of many fishing fleets
and profound anthropogenic changes to the very ecosystems upon which fish-
eries depend.
1
2 Chapter 1
Fig. 1.1 Growth, real and projected, in world capture fisheries production, world fish culture and
population (data from various sources).
Over the next 25 years or so capture fisheries landings might remain stable, pro-
viding appropriate management of stocks and development of new fisheries can
be achieved and providing that novel fish products can be successfully marketed.
All the indications suggest that by the end of the first quarter of the 21st century
farmed fish production will approximate that from capture fisheries production
and be the most important means of providing fish for food. This scenario,
however, takes no account of likely future shortages in some of the raw materials
required for intensive aquaculture and ignores growing constraints on land and
water availability (Beveridge et al.1994b, 1997b; Pauly et al.1998; Naylor et al.
1998, 2000), assuming instead that human ingenuity will rise to the challenges.
1.1 PRINCIPLES OF AQUACULTURE
Fisheries and aquaculture share the same aim: to maximize the yield of useful
organisms from the aquatic environment. The classical theories of Russell (1931)
and Beverton & Holt (1957) have determined that the size of exploitable stocks
is determined by four factors: recruitment rate, growth rate, natural mortality
rate and fishing mortality rate (Fig. 1.2). Capture fisheries try to maximize yields
by increasing fishing mortality rate, partly at the expense of natural mortality,
although if too many fish are killed recruitment and growth are unable to com-
pensate and stocks dwindle. Aquaculture, on the other hand, seeks to increase
yields by manipulation of all four population-regulating factors: growth, repro-
duction, recruitment and natural mortality rates.
Cage Aquaculture – Origins and Principles 3
Fig. 1.2 Factors governing exploitable stock biomass (redrawn from Pitcher & Hart 1982).
Aquaculture began independently in different societies, both agriculture- and
fishing-based, and followed a pattern of development in many respects similar
to that of agriculture. The control of natural mortality through the capture and
holding of fish and shellfish while they increased in biomass or value was prob-
ably an early achievement (Beveridge & Little 2002). The simplest facilities to
construct would have been earth ponds, possibly little more than mud walls built
to temporarily hold water and fish following the seasonal flooding of a river.
Manipulation of growth through feeding with household scraps or agricultural
wastes would have been a logical next step. However, with one or two notable
exceptions, such as that of carp in China (Li 1994), control of spawning and
recruitment is comparatively recent as it is difficult to induce many species to
breed in captivity. There are also many technical problems involved in the hatch-
ing of eggs and the maintenance and feeding of larval and juvenile stages
(Bardachet al.1972). Aquaculture has gradually gained control over all four of
these population-determining processes. Recent decades, in particular, have seen
great advances in the fields of nutrition, genetics, engineering, physiology and
biochemistry, resulting in hugely improved yields.
In summary, aquaculture, or the farming of aquatic organisms, is achieved
through the manipulation of an organism’s life cycle and control of the envi-
ronmental variables that influence it. Three main factors are involved: control
of reproduction, control of growth and elimination of natural mortality agents.
Control of reproduction is essential otherwise farmers must rely on naturally
spawning stocks. The supply of fry from the wild may be restricted to a par-
ticular season and a particular area, and there may also be shortages due to
over-exploitation of wild stocks. This step remains to be realized in the culture
of many, particularly marine, species. Growth can be increased through selec-
tion of broodstock (control of breeding is, therefore, a prerequisite), and through