FINFISH AQUACULTURE DIVERSIFICATION
We would like to honour the memory of our eminent colleague,
Dr Joseph A. Brown, whose enthusiasm for aquaculture diversification
provided inspiration for the book. He was greatly appreciated for his kindness,
accessibility, involvement and impact on a wide range of endeavours.
FINFISH AQUACULTURE
DIVERSIFICATION
EDITED BY
Nathalie R. Le François
Biodôme de Montréal, Québec, Canada
Malcolm Jobling
University of Tromsø, Norway
Chris Carter
University of Tasmania, Australia
Pierre U. Blier
Université du Québec à Rimouski, Québec, Canada
ASSISTANT EDITOR AND ILLUSTRATOR
Arianne Savoie
Université du Québec à Rimouski, Québec, Canada
CABI is a trading name of CAB International
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A catalogue record for this book is available from the British Library, London, UK.
Library of Congress Cataloging-in-Publication Data
Finfish aquaculture diversification / edited by Nathalie R. Le François … [et al.].
p. cm.
Includes bibliographical references and index.
ISBN 978-1-84593-494-1 (alk. paper)
1. Fish culture. I. Le François, Nathalie R. II. Title.
SH151.F46 2010
639.3--dc22
2009015984
ISBN-13: 978 1 84593 494 1
Commissioning editor: Rachel Cutts
Production editor: Fiona Harrison
Typeset by SPi, Pondicherry, India.
Printed and bound in the UK by the MPG Books Group.
Contents
Contributors
Acknowledgements
xvii
xxi
I
Aquaculture Diversification: an Introduction
1
1
Fish Culture: Achievements and Challenges
Malcolm Jobling
3
1.1
1.2
1.3
1.4
1.5
1.6
Introduction
Application of Emerging Technologies to
Aquaculture Research
Stock Improvement
1.3.1 Sex-reversal and production of monosex
populations and triploids
1.3.2 Induction of sterility
1.3.3 Interactions between farmed and wild fish
1.3.4 Transgenic fish
Feed Ingredients and Resources
1.4.1 Feed ingredients of plant origin
1.4.1.1 Transgenic plants
Health Management and Disease Control
1.5.1 Diagnostics and disease treatment
1.5.1.1 Vaccines
1.5.1.2 Antibiotics and other
chemotherapeutic agents
Food Products: Nutritional Composition, Food Safety
and Traceability
1.6.1 Analysis of aquaculture products
3
4
6
7
8
9
10
11
12
12
15
16
17
17
18
19
v
vi
Contents
1.7
1.8
2
Fish Culture: the Rearing Environment
Malcolm Jobling
2.1
2.2
2.3
2.4
2.5
2.6
2.7
3
Fish as Food: Consumer Attitudes (and the Question
of GM-Fish)
Concluding Remarks
Introduction
Water Sources and Their Consequences for
Rearing Systems
2.2.1 Ponds
2.2.2 Cages and pens
2.2.3 Land-based systems
Biosecurity: a Key for Disease Prevention
Water Quality
2.4.1 Salinity
2.4.2 Oxygen
2.4.3 Nitrogenous products: ammonia, nitrite and nitrate
Temperature
2.5.1 Temperature, reproduction and development
Light
Fish Welfare Under Culture Conditions
Fish Culture: Feeds and Feeding
Malcolm Jobling
3.1
3.2
Introduction
Nutrients and Nutritional Requirements
3.2.1 Metabolism and body maintenance: fish versus
terrestrial livestock
3.3 Aqua-feeds for Farming Fish
3.3.1 Feeds for different life history stages
3.3.2 Fishmeal and fish oil: a reduced reliance on these
feed ingredients
3.3.2.1 Organic contaminants in fish and
fish feeds
3.3.2.2 Physiological effects of organic
contaminants
3.3.2.3 Fishmeals as a protein source in
aqua-feeds
3.3.2.4 ‘Alternative’ protein sources in
aqua-feeds
3.3.2.5 The need for marine fish oils in
aqua-feeds
3.4 Feeding Behaviour, Feeding Routines and Feed
Delivery Systems
3.4.1 Feeding methods and routines: assessment
of satiation
21
23
33
33
34
34
36
36
39
40
41
44
45
49
51
53
55
61
61
62
64
66
67
70
71
72
73
74
75
77
77
Contents
vii
3.5
4
Farmed Species and Their Characteristics
Malcolm Jobling
4.1
4.2
4.3
4.4
4.5
4.6
4.7
5
Introduction
Characteristics Desirable in a Farmed Species
Fish as Food: A Comparison with Terrestrial Livestock
Natural Diets of Farmed Animals
Domestication and Genetic Selection
Culture Species
Concluding Comments
Considerations for the Selection and Commercialization
of New or Alternate Species
Nathalie R. Le François, David Otton and Guillaume Werstink
5.1
5.2
5.3
5.4
5.5
5.6
5.7
6
3.4.2 Automatic feeding systems
Environmental Protection and Related Issues
Introduction
Why Develop a New or an Alternate Species?
Who Is Likely To Develop New Species and Products?
When Is This Development Likely To Occur?
What Does the Development Process Entail?
How Should Commercialization Be Conducted?
Conclusion
A Systematic Market Approach to Species Diversification:
a French Case Study
Marc Suquet
6.1
6.2
Introduction
Methodology
6.2.1 Enquiries
6.2.2 Selection procedure
6.3 Constraints and Limitations of the Model
6.4 Case Study: The Case of the French Atlantic, the
Channel and the North Sea Coasts
6.4.1 Enquiries
6.4.2 Selection procedure
7
The Agribusiness Approach
David Otton and Lawrence Dooley
7.1
7.2
7.3
7.4
The Concept of Agribusiness
Method
The Agribusiness System
Case Studies: Catfish, Atlantic Salmon and Barramundi
7.4.1 Channel catfish (Ictalurus punctatus)
7.4.2 Atlantic salmon (Salmo salar)
79
82
88
88
89
91
92
93
94
96
100
100
101
103
105
105
106
112
115
115
118
118
118
119
123
123
125
132
132
132
132
136
137
138
viii
Contents
7.5
7.6
7.4.3 Barramundi (Lates calcarifer)
Conclusion
Future Trends and Issues
139
140
140
II
Finfish Species Description
and Biotechnical Analysis
145
8
Quantitative Approaches for Identifying Finfish Species
Suited for Sustainable and Productive Aquaculture
Nathalie R. Le François, Arianne Savoie and Pierre U. Blier
147
8.1
8.2
Introduction
Site-specific Selection of the Most Suitable Species and
Production Strategy: a Québec (Canada) Case Study
8.2.1 Collection of species-specific biotechnical data
8.2.2 Description of the model
8.2.2.1 Step 1
8.2.2.2 Step 2
8.2.2.3 Step 3
8.2.3 Results and discussion
8.2.4 Particularities, constraints and limitations
of the model
8.3 Evaluation of Commercial Species’ Attributes in Terms of
Productivity/Sustainability
8.3.1 Collection of species-specific biotechnical data
8.3.2 Criteria selection and description
8.3.2.1 Reproduction and incubation
8.3.2.2 Larval and juvenile production
8.3.2.3 On-growing and commercialization
8.3.3 Results and discussion of cold, temperate and
warmwater fish species analysis
8.3.3.1 Coldwater fish species
8.3.3.2 Temperate fish species
8.3.3.3 Warmwater fish species
8.3.4 Particularities, constraints and limitations of
the model
9
147
149
150
150
150
153
153
153
154
155
156
157
157
160
161
165
165
169
172
173
The Sturgeons (Family: Acipenseridae)
Matthew Litvak
178
9.1
9.2
9.3
178
179
180
180
181
182
182
185
General Introduction
Farming of Sturgeons
Shortnose Sturgeon, Acipenser brevirostrum
9.3.1 Biology and culture
9.3.1.1 Gross anatomy
9.3.1.2 Distribution
9.3.1.3 General life history
9.3.1.4 Behaviour/adaptability
Contents
ix
9.4
9.5
9.6
9.7
10
11
12
9.3.1.5 Fishery status
9.3.2 Broodstock management and hatchery operations
9.3.3 On-growing to market size
Atlantic Sturgeon, Acipencer oxyrinchus oxyrinchus
9.4.1 Biology and culture
9.4.1.1 Gross anatomy
9.4.1.2 Distribution
9.4.1.3 General life history
9.4.1.4 Feeding
9.4.1.5 Behaviour/adaptability
9.4.1.6 Fishery status
9.4.1.7 Aquaculture attributes and challenges
9.4.2 Broodstock management and hatchery operations
9.4.2.1 Disease
Product Description
Markets
Future R & D for Shortnose and Atlantic Sturgeons
185
185
187
188
188
188
189
191
191
191
192
192
193
194
194
195
196
Milkfish (Family: Chanidae)
Cheng-Sheng Lee and Chin-fa Liu
200
10.1
10.2
10.3
10.4
10.5
General Introduction
Farming of Milkfish
Broodstock Management and Hatchery Operations
On-growing to Market Size
Future Perspectives
200
201
203
208
212
The Catfish (Family: Ictaluridae)
Jeffrey Silverstein, Terrill Hanson and Brian Bosworth
216
11.1
11.2
11.3
11.4
11.5
General Introduction
Farming of Catfish
Broodstock Management and Hatchery Operations
On-growing to Market Size
Future Perspectives
216
217
219
222
230
The Salmonids (Family: Salmonidae)
Malcolm Jobling, Arne-Mikal Arnesen, Tillman Benfey,
Chris Carter, Ronald Hardy, Nathalie R. Le François,
Robyn O’Keefe, Juha Koskela and Simon G. Lamarre
234
12.1 General Introduction
12.2 Whitefishes: Biology and Culture
12.2.1 Common whitefish, Coregonus lavaretus
12.2.1.1 Farming of common whitefish
12.2.1.2 Broodstock management and
hatchery operations
11.2.1.3 On-growing to market size
234
236
237
239
239
240
x
Contents
13
12.3 Charrs: Biology and Culture
12.3.1 Arctic charr, Salvelinus alpinus
12.3.1.1 Farming of Arctic charr
12.3.1.2 Broodstock management and
hatchery operations
12.3.1.3 On-growing to market size
12.3.2 Brook charr, Salvelinus fontinalis
12.3.2.1 Farming of brook charr
12.3.2.2 Broodstock management and
hatchery operations
12.3.2.3 On-growing to market size
12.3.2.4 Future perspectives
12.4 Atlantic Salmons and Trouts: Biology and Culture
12.4.1 Atlantic salmon, Salmo salar
12.4.1.1 Life cycle of Atlantic salmon
12.4.1.2 Farming of Atlantic salmon
12.4.1.3 Broodstock management and
hatchery management
12.4.1.4 Smolt production
12.4.1.5 On-growing to market size
12.5 Pacific Salmons and Trouts: Biology and Culture
12.5.1 Rainbow trout, Oncorhynchus mykiss
12.5.1.1 Life cycle of rainbow trout
12.5.1.2 Farming of rainbow trout
12.5.1.3 Broodstock management and
hatchery operations
12.5.1.4 On-growing to market size
12.6 Acknowledgements
241
242
245
245
The Codfishes (Family: Gadidae)
Björn Björnsson, Matthew Litvak, Edward A. Trippel
and Marc Suquet
290
13.1 General Introduction
13.2 Atlantic Cod, Gadus morhua
13.2.1 Farming of Atlantic cod
13.2.2 Rearing technologies and practices: full cycle
versus on-growing
13.2.2.1 Capture-based cod farming
13.2.2.2 Full-cycle cod farming
13.2.3 Broodstock management and
hatchery operations
13.2.4 On-growing to market size
13.2.5 Commercialization
13.2.6 Future perspectives
13.3 Haddock, Melanogrammus aeglefinus
13.3.1 Farming of haddock
290
290
294
296
247
248
250
250
252
254
255
255
257
261
261
263
266
271
273
275
275
276
277
281
297
297
298
300
302
303
304
307
Contents
xi
13.3.2
Broodstock management and
hatchery operations
13.3.3 On-growing to market size
13.3.4 Commercialization
13.3.5 Future perspectives
13.4 Pollack, Pollachius pollachius
13.4.1 Farming of pollack
13.4.2 Broodstock management and
hatchery operations
13.4.3 On-growing to market size
13.4.4 Future perspectives
14
15
16
308
309
309
310
310
313
313
313
314
The Snooks (Family: Centropomidae)
Chris Carter, Brett Glencross, Robin S. Katersky
and Michel Bermudes
323
14.1 General Introduction
14.2 Barramundi, Lates calcarifer
14.2.1 Farming of barramundi
14.2.2 Broodstock management and husbandry
14.2.3 On-growing to market size
14.2.4 Commercialization
14.2.5 Future perspectives
323
324
326
327
329
332
333
The Temperate Basses (Family: Moronidae)
Malcolm Jobling, Stefano Peruzzi and Curry Woods
337
15.1 General Introduction
15.2 European Seabass, Dicentrarchus labrax
15.2.1 Seabass biology
15.2.2 Farming of seabass
15.2.3 Broodstock management and
hatchery operations
15.2.4 On-growing to market size
15.2.5 Concluding comments
15.3 Striped Bass, Morone saxatilis, and Striped
Bass Hybrids
15.3.1 Striped bass biology
15.3.2 Farming striped bass and its hybrids
15.3.3 Broodstock management and
hatchery operations
15.3.4 On-growing to market size
15.3.5 Concluding comments
337
338
341
342
343
Seabreams and Porgies (Family: Sparidae)
Malcolm Jobling and Stefano Peruzzi
361
16.1
361
General Introduction
347
349
350
350
351
351
354
356
xii
Contents
17
18
19
16.2 Gilthead Seabream, Sparus aurata
16.2.1 Farming of seabream
16.2.2 Broodstock management and
hatchery operations
16.2.3 On-growing to market size
16.2.4 Concluding comments
362
365
367
Tilapia (Family: Cichlidae)
Kevin Fitzsimmons and Wade O. Watanabe
374
17.1 General Introduction
17.2 Tilapia, Oreochromis sp.
17.2.1 Broodstock management and
hatchery operations
17.2.2 On-growing to market size
17.2.3 Nutrition
17.2.4 Impacts of introductions and farming
17.2.5 Diseases
17.2.5.1 Viral
17.2.5.2 Bacterial
17.2.5.3 Mycotic
17.2.5.4 Parasites
17.2.5.5 Flagellates
17.2.5.6 Ciliates
17.2.5.7 Saltwater parasites
17.2.6 Production and markets for Tilapia
374
375
378
370
372
381
384
386
388
388
388
388
389
389
389
389
389
Drum-fish or Croakers (Family: Sciaenidae)
Juan P. Lazo, Joan G. Holt, Christian Fauvel,
Marc Suquet and Loic Quéméner
397
18.1 General Introduction
18.2 Red Drum, Sciaenops ocellatus
18.2.1 Farming of red drum
18.2.2 Broodstock management and
hatchery operations
18.2.3 On-growing to market size
18.2.4 Conclusion
18.3 Meagre, Argyrosomus regius
18.3.1 Farming of meagre
18.3.2 Broodstock management and
hatchery operations
18.3.3 On-growing to market size
18.3.4 Concluding comments
18.3.5 Conclusion
397
398
400
401
The Wolffishes (Family: Anarhichadidae)
Nathalie R. Le François, Helge Tveiten,
Laura C. Halfyard and Atle Foss
417
402
405
405
408
409
410
412
412
Contents
xiii
19.1
19.2
General Introduction
Spotted Wolffish, Anarhichas minor, and
Atlantic Wolffish, A. lupus
19.2.1 Farming of spotted wolffish
19.2.2 Broodstock management and husbandry
19.2.3 On-growing to market size
19.2.4 Concluding comments
20
21
417
421
422
422
425
427
The Tunas (Family: Scombridae)
Chris Carter, Barbara Nowak and Steven Clarke
432
20.1 General Introduction
20.2 Farming of Tuna, Thunnus sp.
20.3 Atlantic Bluefin Tuna, Thunnus thynnus
20.4 Southern Bluefin Tuna, Thunnus maccoyii
20.5 Pacific Bluefin Tuna, Thunnus orientalis
432
434
435
438
443
The Flatfishes (Order: Pleuronectiformes)
Albert K. Imsland
450
21.1 General Introduction
21.2 Turbot, Scophthalmus maximus
21.2.1 Farming of turbot
21.2.2 Broodstock management and
hatchery operations
21.2.3 On-growing to market size
21.2.4 Commercialization
21.2.5 Future perspectives
21.3 Atlantic Halibut, Hippoglossus hippoglossus
21.3.1 Farming of Atlantic halibut
21.3.2 Broodstock management and
hatchery operations
21.3.3 On-growing to market size
21.3.4 Commercialization
21.3.5 Future perspectives
21.4 Winter Flounder, Pseudopleuronectes americanus
21.4.1 Farming of winter flounder
21.4.2 Broodstock management and husbandry
21.4.3 On-growing to market size
21.4.4 Commercialization
21.4.5 Future perspectives
21.5 Sole, Solea solea and Solea senegalensis
21.5.1 Farming of sole
21.5.2 Broodstock management and hatchery
operations (S. solea)
21.5.3 Broodstock management and hatchery
operations (S. senegalensis)
21.5.4 On-growing of S. solea to market size
21.5.5 On-growing of S. senegalensis to market size
450
454
457
457
459
463
463
464
467
467
469
472
472
473
473
475
476
476
477
478
481
482
483
485
486
xiv
Contents
21.5.6
21.5.7
Commercialization
Future perspectives
487
488
III
Market and Economic Analysis
497
22
Marketing New Species
James A. Young
499
22.1
22.2
22.3
22.4
22.5
22.6
499
501
503
506
508
511
23
Introduction
What is Marketing?
The Fish Marketing Environment
Marketing Decisions on New Species
Planning for New Species and Products
Conclusion
Diversification Pays: Economic Perspectives
on Investment in Diversified Aquaculture
James R. Wilson and Bruno Archer
514
23.1 Introduction
23.2 Economic Reasons for Diversification
23.3 The Political Economics of Aquaculture Diversification
23.4 A Case Study: Application to the Province of Québec
23.4.1 Private venture capital markets and diversified
aquaculture
23.4.2 Public investment strategies
23.5 Concluding Remarks
514
517
520
522
523
524
527
IV
Future Perspectives
531
24
Offshore and Recirculation Technologies
Richard Langan and Michel Couturier
533
24.1 Introduction
24.2 Offshore Technologies
24.2.1 The context for offshore farming
24.2.2 Current status of offshore finfish aquaculture
24.2.2.1 Defining offshore aquaculture
24.2.2.2 Engineering design and
assessment
24.2.2.3 Containment technologies
24.2.2.4 Operational systems
24.2.2.5 Species cultivated in
offshore cages
24.2.2.6 Environmental considerations
24.2.3 Future prospects and challenges
24.3 Recirculation Technologies
24.3.1 Recirculating aquaculture systems (RAS)
533
533
533
534
534
534
535
536
537
538
538
539
539
Contents
xv
24.3.2
24.3.3
24.3.4
25
26
27
Potential of RAS for species diversification
Operation and design
Future prospects and challenges
540
541
542
Valorization of Aquaculture By-products
Pierre U. Blier and Nathalie R. Le François
546
25.1 Introduction
25.2 Feed and Food Use of By-products
25.3 Specialized Products
25.3.1 Enzymes
25.3.2 Antifreeze proteins
25.3.3 Antimicrobial polypeptides
25.4 A Case Study: Wolffish, Anarhichas lupus
and A. minor
25.5 Concluding Remarks
546
548
549
549
550
551
551
Organic and Ecolabelling
James A. Young
556
26.1
26.2
26.3
26.4
26.5
26.6
26.7
556
557
558
560
561
562
564
Introduction
Production Pressures on Diversification
The Role of Branding in Differentiation
Organic Differentiation
Market Impacts of Differentiation
Ecolabelling
Conclusion
553
The Future of Aquaculture: Insights from
Economic Theory
Gunnar Knapp
567
27.1
27.2
27.3
27.4
27.5
27.6
27.7
27.8
27.9
567
567
570
571
574
576
578
582
584
Introduction
Supply and Demand Model
Applying Supply and Demand Modelling to Aquaculture
Modelling How Aquaculture May Change in the Future
Technological Innovation in Aquaculture
The Importance of Marketing for Aquaculture
Effects of Government Policies on Aquaculture
Modelling Diversification of Aquaculture
Conclusions
Species factsheets: Appendix (1–24)
Index
587
661
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Contributors
Bruno Archer, Centre Aquacole de la Côte-Nord (CACN), North-Shore
Aquaculture Center (NSAC), 106 rue Napoléon, Suite 200-B, Sept-Îles
(Québec), Canada G4R 3L7 ([email protected])
Arne-Mikal Arnesen, Nofima A/S, Muninbakken 9–13, Postboks 6122,
N-9291 Tromsø, Norway ([email protected])
Tillman Benfey, Department of Biology, University of New Brunswick, PO Box
4400, Fredericton, New Brunswick, Canada E3B 6E1 ([email protected])
Michel Bermudes Government of Western Australia, Department of Fisheries,
Research Division, PO Box 20, North Beach, WA 6920, Australia
Björn Björnsson, Marine Research Institute, Skulagata 4, 121 Reykjavik,
Iceland ([email protected])
Pierre U. Blier, Département de biologie, chimie et géographie, Université du
Québec à Rimouski, 300 Allée des Ursulines, Rimouski, QC, Canada G5L
3A1 ([email protected])
Brian Bosworth, US Department of Agriculture, Agricultural Research Service,
Catfish Genetics Research Unit, Stoneville, USA
Chris Carter, University of Tasmania, Launceston Campus, Locked bag 1399,
Tasmania 7250, Australia ([email protected])
Steven Clarke, Aquafin CRC, Box 120, Henley Beach, SA 5022, Australia
([email protected])
Michel Couturier, Department of Chemical Engineering, University of New
Brunswick, PO Box 4400, Fredericton, NB, Canada E3B 5A3 ([email protected])
Lawrence Dooley, Department of Management, Centre for Wine, Food and
Agribusiness, Location Room 03, Building N6, Caulfield, Monash
University, Victoria 3800, Australia ([email protected].
edu.au)
xvii
xviii
Contributors
Christian Fauvel, Ifremer, Laboratoire LALR, Station expérimentale de Palavas,
Chemin de Maguelone 34250 Palavas-les-Flôts, France (christian.fauvel@
ifremer.fr)
Kevin Fitzsimmons, Environmental Research Lab, University of Arizona, 2601
E Airport Dr, Tucson, AZ 85706-6985, USA ([email protected])
Atle Foss, Akvaplan-Niva A/S, Bergen office, PO Box 2026, Nordnes 5,
N-5817, Bergen, Norway ([email protected])
Brett Glencross Government of Western Australia, Department of Fisheries,
Research Division, PO Box 20, North Beach, WA 6920, Australia (Brett.
[email protected])
Laura C. Halfyard, Marine Institute, Memorial University of Newfoundland,
PO Box 4220, St John’s, Newfoundland, Canada A1C 5R3 ([email protected])
Terrill Hanson, Department of Fisheries and Allied Aquacultures, Auburn University, 203 Swingle Hall, Auburn, AL 36849, USA ([email protected])
Ronald Hardy, UI Hagerman Fish Experiment Station, 3059 F National Fish
Hatchery Road, Hagerman, Idaho 83332, USA ([email protected])
Joan G. Holt, University of Texas at Austin, Marine Science Institute, 750
Channel View Drive, Port Aransas, TX 78373-5015, USA ( joan@utmsi.
utexas.edu)
Albert Imsland, Akvaplan-Niva A/S, Iceland Office, Akralind 4, 201 Kópavogi,
Iceland and Department of Biology, University of Bergen, High Technology
Centre, 5020 Bergen, Norway ([email protected])
Malcolm Jobling, University of Tromsø, 9037 Tromsø, Norway (malcolm.
[email protected])
Robin Katersky University of Tasmania, Locked bag 1370, Launceston, TAS
7250, Australia ([email protected])
Gunnar Knapp, Institute of Social and Economic Research, University of
Alaska Anchorage, 3211 Providence Drive, Anchorage, Alaska 99508
([email protected])
Juha Koskela, Finnish Game and Fisheries Research Institute, Laukaa Fisheries
Research and Aquaculture, 41360 Valkola, Finland ( [email protected])
Simon G. Lamarre, Memorial University of Newfoundland, Canada (simon.
[email protected])
Richard Langan, Atlantic Marine Aquaculture Center, University of New
Hampshire, Gregg Hall, 35 Colovos Road, Durham, NH 03824, USA
([email protected])
Juan P. Lazo, CICESE, Carretera Tijuana – Ensenada CP 22860, Ensenada,
BC Mexico ([email protected])
Nathalie R. Le François, Biodôme de Montréal, 4777 Avenue Pierre-De
Coubertin, Montréal, Québec H1V 1B3, Canada and Université du
Québec à Rimouski, 300 des Ursulines, Rimouski, QC, G5L 3A1, Canada
([email protected])
Cheng-Sheng Lee, Center for Tropical and Subtropical Aquaculture Oceanic
Institute, 41–202 Kalanianaole Highway, Waimanalo, HI 96795, USA
([email protected])
Contributors
xix
Matthew Litvak, Centre for Coastal Studies and Aquaculture and Department
of Biology, University of New Brunswick, P.O. Box 5050, Saint John,
New Brunswick, Canada E2L 4L5 ([email protected])
Chin-fa Liu, Consultant for Team Aqua Corporation, 14 Floor-1, No. 115,
Jungshan Road, Shinying City, Tainan, Taiwan, 730, ROC (teamaqua@
ms13.hinet.net)
Barbara Nowak, School of Aquaculture, University of Tasmania, Launceston,
Australia ([email protected])
Robyn O’Keefe, Department of Biology, University of New Brunswick, PO Box
4400, Fredericton, New Brunswick, Canada E3B 5A3 ([email protected])
David Otton, 23 Thompson Drive, Tathra, New South Wales, Australia 2550
([email protected])
Stefano Peruzzi, University of Tromso, 9037 Tromsø, Norway (stefanop@nfh.
uit.no)
Loic Quéméner, Ifremer, Centre de Brest, BP70, 29280 Plouzané, France
([email protected])
Arianne Savoie, Université du Québec à Rimouski, 300 des Ursulines,
Rimouski, QC, G5L 3A1, Canada ([email protected])
Jeffrey Silverstein, USDA/ARS National Center for Cool and Cold Water
Aquaculture, 11861 Leetown Road, Kearneysville, WV 25430, USA
( [email protected])
Marc Suquet, Ifremer, Laboratoire ARN, Station Expérimentale d’Argenton,
Presqu’île du Vivier, 29840 Landunvez, France ([email protected])
Edward A. Trippel, St Andrews Biological Station, 531 Brandy Cove, St Andrews,
New Brunswick, Canada E5B 2L9 ([email protected])
Helge Tveiten, Nofima A/S, Muninbakken 9–13, Postboks 6122, N-9291
Tromsø, Norway ([email protected])
Wade O. Watanabe, Centre of Marine Science, University of North Carolina
at Wilmington, 7205 Wrightsville Ave, Wilmington, NC 28403, USA
([email protected])
Guillaume Werstink, Université du Québec à Rimouski, 300 des Ursulines,
Rimouski, QC, G5L 3A1, Canada ([email protected])
James R. Wilson, Département Économie et de Gestion, Université du Québec
à Rimouski, 300 Allée des Ursulines, Rimouski, QC, Canada G5L 3A1
([email protected])
Curry Woods, Department of Animal and Avian Sciences University of
Maryland College Park, MD 20742, USA ([email protected])
James A. Young, Department of Marketing, University of Stirling, Stirling FK9
4LA, Scotland, UK ( [email protected])
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Acknowledgements
We would like to thank the following people:
Brian Colwill and Dr David Otton for their assistance with linguistic verification. David came to aquaculture as a mature aged PhD student and his
single minded advocacy for the agribusiness approach and his enthusiasm
for aquaculture will be greatly missed in Australia and beyond;
Marc Veillet and Karine Bisson of the Ministère de l’Agriculture, des Pêcheries
et de l’Alimentation du Québec;
Dr Céline Audet (ISMER/UQAR, Québec, Canada) for reviewing the winter
flounder section, Dr Denis Coves (Ifremer, France) for fruitful exchange
on tuna cultivation efforts in Europe and Dr Serge Parent (Biodôme de
Montréal, Québec, Canada) for his constructive comments;
François Larouche, Timothée Govarre and Sarah Tremblay-Bourgeois for
punctual, highly specific tasks that provided relief when most needed.
The financial contributions of the Université du Québec à Rimouski and the
Biodôme de Montréal are also acknowledged.
xxi
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I
Aquaculture Diversification:
an Introduction
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1
Fish Culture: Achievements
and Challenges
MALCOLM JOBLING
University of Tromsø,Tromsø, Norway
1.1
Introduction
Aquaculture is the cultivation of aquatic organisms (e.g. algae, molluscs, crustaceans, fish) and implicit in this is human intervention that involves some control
over the stock. The degree of human intervention may be limited in extensive
culture of algae and molluscs and in extensive pond culture of fish and crustaceans, but the level of control exerted is high in intensive farming systems.
Intensive culture involves intervention at all phases of the production cycle; from
broodstock maintenance and egg production to the harvesting and marketing of
the finished product (Fig. 1.1). The farmed animals are reared in captivity
throughout their lives; they are held under relatively benign, semi-controlled
conditions and rely on formulated feeds for their nutrition. Aquaculture research
and development (R & D), as it relates to intensive fish farming, currently encompasses all aspects of production and postharvest processing, including culture
unit design, feed delivery systems, water treatment, feed formulation and disease diagnosis and treatment. There is a growing perception that intensive
aquaculture is a modern industry; this industry is becoming subject to increased
scrutiny by policy makers and the general public and is becoming increasingly
influenced by social attitudes that have an impact on regulations, marketing and
product ranges and acceptability (Beardmore and Porter, 2003; Lee, 2003;
Aerni, 2004; Kelso, 2004; Boyd et al., 2005; Focardi et al., 2005; Foran
et al., 2005; Logar and Pollock, 2005; Midtlyng, 2005; Muir, 2005; Myhr and
Dalmo, 2005; Naylor et al., 2005; Verbeke et al., 2005; Devlin et al., 2006;
Huntingford et al., 2006).
Intensive fish culture is benefiting from increased use of sophisticated
instrumentation and management tools, and modern analytical techniques are
finding increased application in aquaculture R & D. In the sections that follow,
examples will be given of the ways in which some of these recently developed
©CAB International 2010. Finfish Aquaculture Diversification
(eds N.R. Le François, M. Jobling, C. Carter and P.U. Blier)
3
4
M. Jobling
Broodstock
Gametes
(eggs and sperm)
Larvae and juveniles
Feeds
and
feeding
Grow-out
to market size
Animal improvement
Selective breeding
Sex reversal
Genetic biotechnologies
Harvesting
and
processing
Water and waste treatment
Water inflow
Wastewater
and effluent
Distribution
and sales
Fig. 1.1. Overview of the production cycle of farmed fish with an indication of the
areas in which there is human intervention.
techniques have been used to address research problems with direct bearing on
intensive aquaculture. There will also be consideration of some of the challenges and contentious issues that the industry must face.
1.2 Application of Emerging Technologies
to Aquaculture Research
In recent years, there have been major advances in a variety of analytical
methods and molecular technologies. For example, molecular diagnostics can
play a key role in the detection and identification of food contaminants and
allergens, potential pathogens and genetically modified organisms (GMOs).
Within this sphere, DNA microarray technology has created the possibility for
simultaneous analysis of large gene sets, making it a potent molecular diagnostics tool with a number of applications (Liu-Stratton et al., 2004; Kato et al.,
2005; Roy and Sen, 2006). As such, the development of molecular diagnostics
techniques has had major impacts on R & D in a host of applied sciences,
including clinical (human) and veterinary medicine, food science, agronomy
and agricultural sciences.
These disciplines interface with aquaculture across a broad range of subject
areas; genetics and selective breeding, health management and disease treatment, authentication and control of feed ingredients, postharvest processing,
product storage and spoilage, assurance of food safety, product development
and identification and traceability of products through the food chain (Blanco and
Villarroya, 2002; Cozzolino et al., 2002, 2005a,b; Ali et al., 2004; Carbonaro,
2004; Dunham, 2004; Huss et al., 2004; Kuiper et al., 2004; Pérez-Marin
Achievements and Challenges
5
et al., 2004; Deisingh and Badrie, 2005; Focardi et al., 2005; Gorris, 2005;
Guérard et al., 2005; Kelly et al., 2005; Lehrer and Bannon, 2005; Midtlyng,
2005; Monis et al., 2005; Neira and Diaz, 2005; Pinotti et al., 2005; Verbeke
et al., 2005; Adams and Thompson, 2006; Berrini et al., 2006; Bruhn and
Earl, 2006; Gasser, 2006; Reid et al., 2006; Toldrá and Reig, 2006). Similar
sets of methods, such as spectroscopy (e.g. near-infrared (NIR), mid-infrared
(MIR), UV-, Raman-, nuclear magnetic resonance (NMR) spectroscopy), immunological assays and DNA-based technologies, are being applied increasingly to
assist in the solving of research problems in medical science, food science, agriculture and livestock production and aquaculture.
Of the spectroscopic techniques, NIR spectroscopy has attained popularity
because it is a rapid and non-destructive technique, equipment costs are relatively low and the equipment is quite easy to use. Thus, interest in the exploitation of the analytical potential of NIR paralleled the development of electronic
optical equipment and computers that were capable of rapid extraction and
processing of the information contained within NIR spectra. NIR spectroscopy
can be used on both solid and liquid samples without any major pretreatment,
and interpretation of the spectra can give information about both the physical
and chemical properties of the sample (Blanco and Villarroya, 2002; Reid
et al., 2006). It currently has use as a rapid analytical tool in quality control in
the petrochemical and pharmaceutical industries and as an aid in diagnostics in
the clinical and biomedical fields, but NIR spectroscopy has widest application
in the food science and animal feed sectors. NIR spectroscopy is, for example,
used for determining chemical composition (protein, moisture and oil/fat) of
feed ingredients and feeds and of crops and livestock, either prior to or at harvest/slaughter, and may also be used for identification and authentication purposes (Blanco and Villarroya, 2002; Cozzolino et al., 2002, 2005a,b;
Pérez-Marin et al., 2004; Reid et al., 2006).
As a second example, the development of molecular marker techniques
created new possibilities for the identification and genetic characterization of
species, populations and individuals. This has important implications for the
study of interrelationships between species (taxonomy and phylogeny), population genetics, selective breeding and genetics and disease diagnosis (Melamed
et al., 2002; Ali et al., 2004; Dunham, 2004; Deisingh and Badrie, 2005;
Gjedrem, 2005; Guérard et al., 2005; Monis et al., 2005; Neira and Diaz,
2005; Pinotti et al., 2005; Adams and Thompson, 2006; Chistiakov et al.,
2006; Gasser, 2006). Methods involving the polymerase chain reaction (PCR)
to amplify nucleic acids have proven particularly valuable and have been applied
to several types of research problem. PCR, which has been in use for almost
20 years, is a fundamental technology for genetic identification and characterization. DNA markers derived from PCR amplification are now being widely
used for genetic characterization and for distinguishing between genetic variants at different hierarchical levels: species, populations, strains and individuals
(Ali et al., 2004; Dunham, 2004; Liu and Cordes, 2004; Gjedrem, 2005;
Neira and Diaz, 2005; Chistiakov et al., 2006; Reid et al., 2006; Renshaw
et al., 2006). Major advantages of PCR over alternative techniques for nucleic
acid amplification are cost and ease of use. Using PCR, enzymatic amplification
6
M. Jobling
of either mitochondrial or genomic DNA can be achieved in vitro from minute
amounts of material. Highly conserved DNA regions can be used to delineate
taxonomic relationships between species, examination of moderately conserved regions can be used to distinguish between populations, whereas variable DNA regions can be used for tracking individuals and ‘mapping’ can be
used to identify genetic markers that correlate genotype to phenotype, for
example, linked to important production traits. The latter finds application in
the identification of molecular markers of qualitative and quantitative trait loci
(QTLs) of economic interest (Melamed et al., 2002; Ali et al., 2004; Dunham,
2004; Liu and Cordes, 2004; Neira and Diaz, 2005; Chistiakov et al., 2006).
Thus, PCR encompasses amplification of a conserved region of mDNA for
species identification as in PCR-RFLP, or a fingerprinting approach using
PCR-RAPD for the detection of genetic variation or the definition of genetic
markers.
1.3
Stock Improvement
Farmed stock can be improved by selective breeding and/or by implementing
a variety of genetic biotechnologies (Maclean and Laight, 2000; Lee, 2001;
Devlin and Nagahama, 2002; Melamed et al., 2002; Utter and Epifanio,
2002; Beardmore and Porter, 2003; Fjalestad et al., 2003; Dunham, 2004;
Liu and Cordes, 2004; Gjedrem, 2005; Mignon-Grasteau et al., 2005; Neira
and Diaz, 2005; Chistiakov et al., 2006; Goetz et al., 2006). DNA marker
methods, and other genetic technologies, are having increased impact on the
improvement of production characteristics of aquaculture stock and they find
application in broodstock management and selective breeding programmes.
For example, several fish species are currently under study for genome sequencing (Dunham, 2004; Volff, 2005; Goetz et al., 2006) and some commercially
important species have been included in such investigations. These include
channel catfish, Ictalurus punctatus, Atlantic salmon, Salmo salar, rainbow
trout, Oncorhynchus mykiss, and Nile tilapia, Oreochromis niloticus (Fjalestad
et al., 2003; Dunham, 2004; Volff, 2005), where the focus has been on the
identification of QTLs of economic interest. Such QTLs relate to those with an
influence on growth, age-at-maturation and reproductive characters, body form
and pigmentation, environmental tolerances, disease resistance and behaviour
(Fjalestad et al., 2003; Dunham, 2004; Liu and Cordes, 2004; Gjedrem,
2005; Neira and Diaz, 2005; Volff, 2005; Chistiakov et al., 2006), and identified markers are being used to assist with broodstock selection for inclusion in
breeding programmes.
Genetic interventions, environmental manipulations and hormonal treatments, either alone or in combination, may be used to influence sex determination, sexual differentiation and reproductive physiology and behaviour (Lee,
2001; Patiño, 2002; Melamed et al., 2002; Kagawa et al., 2003; Dunham,
2004; Gjedrem, 2005; Neira and Diaz, 2005; Goetz et al., 2006; see
Chapter 2, this volume). For example, photothermal manipulations are used to
influence the onset of sexual maturation (timing of puberty) and are employed
Achievements and Challenges
7
in broodstock management for production of out-of-season eggs. In addition,
hormone treatments are used to induce gamete maturation and spawning in a
wide range of species.
1.3.1
Sex-reversal and production of monosex populations and triploids
Genetic techniques, involving a sex-reversal step, can be used to produce
single-sex (monosex) populations and gene manipulation may be employed to
induce sterility through triploidization (Fig. 1.2). The production of monosex
(single-sex) populations may be desirable when there are differences between
the sexes in growth rate, age and size at maturity, disease resistance and other
production characters, e.g. coloration, flesh characteristics, etc. The rearing of
monosex populations may also be used to prevent unwanted (uncontrolled)
spawning in rearing units such as ponds. The raising of sterile fish may be
desirable as a measure to eliminate spawning in the farmed population and to
reduce the potential negative genetic effects of farm escapees on natural populations (due to interbreeding).
Production of sterile fish may be used to reduce the negative effects of sexual maturation on growth and prevent the deterioration of flesh quality (due to
the mobilization of reserves from the muscle) that accompanies maturation in
Broodstock
Androgen treatment
at low dosage
Young juveniles
Genotypic female
Phenotypic male
'Female'
sperm
Genotypic female
fertilized eggs
Pressure or thermal
shock shortly after
fertilization
Monosex
(all-female)
triploids
Normal (female)
ova
Phenotypic female
Genotypic female
Broodstock
Monosex
(all-female)
diploids
Grow out
Diploids harvested
and marketed before
they mature
Fig. 1.2. Schematic representation of sex-reversal techniques and the methods used
to produce monosex (all female) diploid and triploid fish. In this scheme, it is assumed
that the female is the homogametic (XX) sex and the male is the heterogametic (XY)
sex. Sex reversal is induced by treating fertilized eggs, or very young juveniles, with
male sex steroid hormones (androgens). Triploidy is induced by subjecting fertilized
eggs to a temperature or a pressure shock.
8
M. Jobling
many fish species. Muscle protein degradation involves three major proteolytic
enzyme systems: the lysosomal cathepsins, the calpain–calpastatin (calpain–
CAST) system and the ubiquitin–proteasome system (Salem et al., 2004,
2005a,b, 2006). Enzymes of these three systems are expressed differently in
fertile diploid and sterile triploid rainbow trout, O. mykiss, with the cathepsins
seemingly playing the major role in the proteolysis of muscle proteins seen in
maturing fish. On the other hand, the calpain–CAST system appears to play an
important role in the regulation of muscle protein turnover during growth and in
the mobilization of reserves that occurs under a fast. This system, along with the
cathepsins, is also involved in the degradation of muscle proteins that occurs
post-mortem, thereby having an influence on muscle softening, textural changes
and fillet ‘quality’ (Salem et al., 2004, 2005a,b, 2006).
Although methods used for producing monosex and/or sterile populations
are now considered routine for several species, they do not have universal
application due to the fact that several anomalous effects have been observed.
Anomalies may arise, for example, if the eggs and hatchlings are exposed to
waters of particular temperatures or with certain chemical characteristics
(Devlin and Nagahama, 2002; Patiño, 2002; Kagawa et al., 2003; Miyamoto
and Burger, 2003; Mills and Chichester, 2005; Goto-Kazeto et al., 2006; see
Chapter 2, this volume). This is seen in intensive commercial production of
European seabass, Dicentrarchus labrax, in which about 75% of the farmed
fish usually develop as males; male-biased populations are undesirable because
males grow more slowly and mature earlier than females. A substantial proportion of the male fish mature before reaching harvest size, so production of
monosex female populations would be desirable. Although sex manipulation of
seabass has been achieved by exposing fish to exogenous sex steroid hormones, efforts to produce female monosex seabass populations using crosses
involving sex-reversed individuals have not met with success. A major stumbling
block for the application of sex-reversal techniques to this species is that the
mechanisms responsible for sex determination and differentiation are not
known with certainty (Piferrer et al., 2005).
1.3.2
Induction of sterility
Chromosomal manipulation methods are useful for the production of triploid
and tetraploid individuals, but they are not 100% successful. Consequently, the
populations produced inevitably will contain a small percentage of fertile diploids. It is possible to induce sterility via the production of hybrids and by other
methods. The biotechnological methods involve the production of individuals
that express antagonists for a function needed for fertility, suppression of development and differentiation of germ cells, or suppression of the expression of
genes required for the biosynthesis of sex steroid hormones (Maclean and
Laight, 2000; Melamed et al., 2002; Kagawa et al., 2003; Weidinger et al.,
2003; Dunham, 2004; Slanchev et al., 2005). For example, research into
primordial germ cell (PGC) development and function has given promising
results (Raz, 2003; Weidinger et al., 2003; Slanchev et al., 2005). PGCs are
Achievements and Challenges
9
the cells that ultimately give rise to the gametes, but these cells do not have
their source in the embryonic tissue that develops into the gonads. In other
words, PGCs initially migrate from their source to the genital ridges of the
developing embryo and there is then differentiation of the gonads. Over time,
the PGCs differentiate into eggs or sperm in the ovary or testis, respectively
(Raz, 2003). Work carried out on zebrafish, Danio rerio, provides evidence of
a key role of PGCs in sex determination and gonad differentiation. Ablation of
PGCs in embryonic zebrafish gave rise to sterile adults, all of which were males
(as assessed using morphological and behavioural criteria, including courtship
and mating with females) (Slanchev et al., 2005). This research may pave the
way for similar studies on commercially farmed fish species, with the aim of
producing sterile populations. Such populations might have better growth and
production characteristics than fertile conspecifics and sterility could also reduce
the potential impact of farm escapees on wild populations.
PGCs may be transplanted from one species to another and preliminary
data provide evidence that this method can be used to develop surrogate broodstock that produce xenogenic donor-derived offspring (Takeuchi et al., 2004).
Further, the germ cells may retain a high degree of developmental plasticity even
after the commencement of differentiation (Okutsu et al., 2006). For example,
testicular germ cells taken from the testes of mature rainbow trout, O. mykiss,
and transplanted into undifferentiated embryonic gonads were shown to have
retained developmental plasticity. These cells were capable of displaying sexual
bipotency. In other words, the testicular germ cells developed into spermatozoa
in male embryonic recipients, but differentiated into eggs when the recipient
embryonic rainbow trout were females (Okutsu et al., 2006). This demonstrated
that the differentiation and development of the testicular germ cells was not
autonomous and hard-wired, but could be controlled and directed by the environment to which the cells were exposed. In addition, the gametes, either sperm
or eggs, derived from the transplanted testicular germ cells were fully functional
and could be used for the production of viable offspring (Okutsu et al., 2006).
These approaches to producing functional eggs and sperm offer a powerful tool
for the study of gamete differentiation and development in fish and may also
have potential for the rapid production of inbred strains that express a range of
commercially desirable genetic characters.
1.3.3
Interactions between farmed and wild fish
Although the production of sterile farmed stock might eliminate problems related
to the genetic impacts of farm escapees on natural populations, it would not
serve to eliminate all forms of interaction. Individuals that escape from farms
could be members of non-native or introduced species, highly selected domesticated stocks, hybrids or animals that have had their genetic constitutions altered
using transgenic biotechnologies (genetically modified organisms – GMOs).
These different categories of exotics have different characteristics and have the
potential to impact wild populations in several ways. The farm escapees could
act as either predators or prey, they could be vectors of parasites or disease
10
M. Jobling
organisms and they could compete for food or other habitat resources, resulting
in displacement or exclusion of native species and natural populations. In the
case of the farm escapees being fertile, there could also be interbreeding or
hybridization between the exotics and native stocks, resulting in changes to
genetic constitution or sterility. In all likelihood, several of these mechanisms
would act simultaneously (Beardmore and Porter, 2003; Aerni, 2004; Bessey
et al., 2004; Devlin et al., 2004, 2006; Kelso, 2004; Muir, 2004; Welcomme
and Craig, 2004; Bondad-Reantaso et al., 2005; Boyd et al., 2005; Logar and
Pollock, 2005; Murray and Peeler, 2005; Naylor et al., 2005; Bekkevold et al.,
2006; Jonsson and Jonsson, 2006; Wessel et al., 2006).
1.3.4 Transgenic fish
Hitherto, over 30 species of fish have been the subject of transgenic research
and genetic engineering, and the species studied include several representatives from the major farmed groups of fishes – the carps, tilapias, catfishes and
salmonids. Transgenesis may be used to obtain basic information on gene function and regulation, but also has commercial application in the improvement of
animal production and in the introduction of gene constructs that result in the
biosynthesis of high-value products such as recombinant proteins (Beardmore
and Porter, 2003; Houdebine, 2005). The application of transgenic technology in fish has been concerned mostly with the examination of methods that
can be used to enhance the growth of farmed stock, predominantly via the
transfer of genes coding for growth hormone (Maclean and Laight, 2000;
Beardmore and Porter, 2003; Dunham, 2004; Muir, 2004; Houdebine, 2005;
Logar and Pollock, 2005; Devlin et al., 2006), but additional possibilities exist
for exploitation of this type of genetic manipulation. For example, gene constructs may be introduced to enhance disease resistance or modify metabolic
pathways that have influences on the chemical composition of the flesh
(Beardmore and Porter, 2003; Devlin et al., 2006).
One such example is the modification of fatty acid metabolic pathways to
enhance the biosynthesis of n-3 highly unsaturated fatty acids (n-3 HUFAs) and
increase their deposition in the flesh of the farmed animal (Alimuddin et al.,
2005). The biosynthesis of HUFAs depends on a series of fatty acid desaturation and elongation reactions that are catalysed by a number of enzymes (Fig.
1.3). Fish species differ in their abilities to carry out the desaturation and elongation reactions and the characteristics of the enzymes differ among species
(Zheng et al., 2004; Agaba et al., 2005; Robert, 2006). Most notably, there
are differences between carnivorous marine species and herbivorous and omnivorous freshwater fish species in the ability to synthesize HUFAs from the 18C
precursor fatty acids. Genes coding for key enzymes in the n-3 HUFA biosynthetic pathway may be introduced into the fish genome and fatty acid metabolic
pathways modified accordingly (Alimuddin et al., 2005). There is, however, the
possibility that introduction of novel DNA into the fish genome could give rise
to unintended side effects, such as overexpression of some genes and the silencing of others; the examination of unintended side effects of genetic engineering
in fish is in its infancy, although metabolomics and other ‘omics-based’ methods
Achievements and Challenges
Enzyme
∆9 desaturase
∆6 desaturase
elongase
∆5 desaturase
elongase
11
Fatty acid series
n-7
n-9
16:0
18:0
n-6
n-3
↓
↓
16:1 n-7
18:1 n-9
18:2 n-6
18:3 n-3
↓
↓
↓
↓
16:2 n-7
18:2 n-9
18:3 n-6
18:4 n-3
↓
↓
↓
↓
18:2 n-7
20:2 n-9
20:3 n-6
20:4 n-3
↓
↓
↓
↓
18:3 n-7
20:3 n-9
20:4 n-6
20:5 n-3
↓
↓
↓
↓
20:3 n-7
22:3 n-9
22:4 n-6
22:5 n-3
↓
↓
24:4 n-6
24:5 n-3
↓
↓
24:5 n-6
24:6 n-3
elongase
∆6 desaturase
(β-Oxidation)
↓
↓
22:5 n-6
22:6 n-3
Fig. 1.3. Pathways for chain elongation and desaturation of fatty acids. Fatty acids
of the n-7 and n-9 series can be synthesized de novo, whereas fatty acids of the
n-6 and n-3 series are the essential fatty acids. The ∆6 desaturase enzyme has a
preference for unsaturated fatty acids as substrate. In the absence of 18:3 n-3 and
18:2 n-6, 18:1 n-9 is desaturated and elongated, leading to an accumulation of
long-chain fatty acids of the n-9 series in tissues (this can be used as an indication
of essential fatty acid deficiency). Carnivorous marine fish species seem to have low
∆5 desaturase activity and they have a low capacity to use the n-3 and n-6 18C fatty
acids as precursors for synthesis of n-3 and n-6 HUFAs. The shorthand notations of
the fatty acids give information about the number of carbon atoms, the number of
double bonds and the position of the first double bond from the methyl end of the
molecule (from Jobling, 2004c).
for carrying out such investigations are available (Beardmore and Porter, 2003;
Kuiper et al., 2004; Liu-Stratton et al., 2004; Kato et al., 2005; Griffin, 2006;
Rischer and Oksman-Caldentey, 2006; Viant et al., 2006).
1.4
Feed Ingredients and Resources
Developments in plant breeding and genetics are playing an increasingly important role in the provision of ingredients for aqua-feeds. Although a wide range
of ingredients is used in the formulation of aqua-feeds (Hertrampf and
Piedad-Pascual, 2000), fishmeals and fish oils traditionally have been used as
12
M. Jobling
major ingredients, but in recent years there has been a trend towards an
increased reliance on plant-based products (see Chapter 3, this volume).
Fishmeals have been used as a major ingredient because they have been a
widely available source of protein of high quality. Marine fish oils have been
widely used as the main lipid source in aqua-feeds because they have been
readily available, relatively cheap and are an excellent source of the n-3 HUFAs
deemed beneficial for human health (Graham et al., 2004; Ruxton et al.,
2004, 2005; SACN-FSA, 2004; Bergé and Barnathan, 2005; Bourre, 2005;
Cleland et al., 2005; MacRae et al., 2005; Napier and Sayanova, 2005;
Bethune et al., 2006; Kim and Mendis, 2006). The heavy reliance on fishmeals and oils as major ingredients in aqua-feeds has, however, been questioned and criticized (Naylor et al., 2000; Muir, 2005). Stocks of small, pelagic
fish used for fishmeal and oil production represent finite resources that are
either fully exploited or are being overexploited and are at risk of collapse.
Fears have also been expressed that fishmeals and oils may give rise to contamination of the flesh of farmed fish with organochlorine compounds and/or
heavy metals (Easton et al., 2002; Jacobs et al., 2002; Hites et al., 2004; Bell
et al., 2005; Berntssen et al., 2005; Carlson and Hites, 2005; Foran et al.,
2005; Hamilton et al., 2005; Bethune et al., 2006; Montory and Barra,
2006). These contaminants may be carcinogenic and may give rise to developmental anomalies that result in the malformation of various tissues and organs
in both fish and human consumers (Miyamoto and Berger, 2003; Sumpter and
Johnson, 2005; Scott et al., 2006; see Chapter 3, this volume).
1.4.1
Feed ingredients of plant origin
There may be major benefits to be gained by including protein sources of plant
origin in fish feeds, but there are also problems associated with such feed
sources (Hertrampf and Piedad-Pascual, 2000; McKevith, 2005). For example, many plants are deficient in some essential nutrients, such as some amino
acids (e.g. lysine and methionine). This means that there may be a need to add
amino acid supplements to feeds prepared with protein sources derived from
plants. In addition, most plants contain antinutritional factors (ANFs) that interfere with digestion and absorption, reduce nutrient bioavailability and feed utilization and may have other adverse effects (Table 1.1) (Francis et al., 2001;
Jobling, 2004c; Acamovic and Brooker, 2005). Further, it is becoming increasingly difficult to obtain vegetable feed ingredients, for example, soya, maize
and canola, guaranteed to be free from some form of biotechnological genetic
modification, i.e. non-transgenic vegetable feed ingredients are becoming
increasingly scarce in the global market (Kok and Kuiper, 2003; Flachowsky
et al., 2005; Myhr and Dalmo, 2005; Bruhn and Earl, 2006).
1.4.1.1 Transgenic plants
The genetic modification of plants may involve the introduction of genes encoding for increased disease resistance, production of insecticidal proteins or
Antinutritional factor (ANF)
Enzyme inhibitors
Protease Amylase Phytate
‘Oilseed’ meals
Soybean
Rape/canola
Cottonseed
Sunflower
Sesame
¥
¥
¥
×
×
×
Phyto-oestrogens Saponins Tannins Lectins
×
×
×
×
×
×
×
×
¥
¥
Legumes
Lupin
Lucerne
Faba bean
¥
‘Grains’
Maize
Wheat
Sorghum
¥
¥
¥
‘Tubers’
Potato
Cassava
¥
¥
¥
×
¥
¥
×
×
×
¥
×
×
×
×
×
Alkaloids Cyanogens Glucosinolates
Achievements and Challenges
Table 1.1. Overview of major classes of antinutritional factors (ANFs) present in plants used as protein and/or carbohydrate sources in feeds
prepared for farmed fish. × indicates that the ANF is present and heat-labile ANFs (i.e. ANFs that can be destroyed or denatured by heat
treatment) are shown in bold typeface (from Jobling, 2004c).
¥
×
×
×
×
×
×
¥
×
¥
¥
¥
×
×
×
13
14
M. Jobling
increased herbicide tolerance; the agents that impart these properties are
present at very low concentration and have little influence on the gross composition of the plant. Alternatively, attempts may be made to influence nutritional
value by increasing the protein content or indispensable (essential) amino acids,
increasing concentrations of vitamins, such as tocopherols, or by reducing concentrations of ANFs (Tucker, 2003; Flachowsky et al., 2005; Lehrer and
Bannon, 2005; Bruhn and Earl, 2006; Dalal et al., 2006).
Plant oils are generally deficient in n-3 HUFAs, although several contain
relatively high concentrations of 18C n-3 precursors (Hertrampf and PiedadPascual, 2000; McKevith, 2005; Robert, 2006). The fatty acid compositions
of the flesh of monogastric animals frequently reflect the compositions of the
feed, so aquaculture species given feeds based on plant oils may have relatively low concentrations of n-3 HUFAs in their flesh (e.g. Jobling, 2004a,b,c;
Wonnacott et al., 2004; Berntssen et al., 2005; Torstensen et al., 2005;
Visentainer et al., 2005; see Chapter 3, this volume). Given this, one major
area of research focus has been the elucidation and modification of the metabolic pathways of fatty acid synthesis, with the aim of producing plants with
higher n-3 HUFA content. The conventional metabolic pathway for the synthesis of the HUFAs is via the n-3 pathway employing the ∆6 desaturase and
elongase route (Fig. 1.3), but there are alternative pathways. One of the alternatives involves the n-6 pathway and a ∆17 desaturase (C20:4 n-6 → 20:5
n-3), another involves the n-3 pathway and a ∆4 desaturase (C22:5 n-3 →
22:6 n-3) and there is also a route that relies on the n-3 pathway and ∆9
elongase and ∆8 desaturase (C18:3 n-3 → 20:3 n-3 → 20:4 n-3). The alternative pathways, found in some unicellular organisms, appear to offer most
promise with regard to introduction into higher plants (Abbadi et al., 2004;
Graham et al., 2004; Domergue et al., 2005; Flachowsky et al., 2005;
Napier and Sayanova, 2005; Guschina and Harwood, 2006; Napier et al.,
2006; Robert, 2006).
Animal feeds, including aqua-feeds, may also be supplemented with n-3
HUFAs obtained by microbial fermentation (Ward and Singh, 2005; Spolaore
et al., 2006). The best microbial sources of these fatty acids are unicellular
algae, or algal-like protists, of the order Thraustochytriales. Industrial fermentation methods have been developed for several species and/or strains of
Thraustochytrium and Schizochytrium (Bergé and Barnathan, 2005; Ward
and Singh, 2005). Although plants can be engineered to produce n-3 HUFAs,
microorganisms have certain advantages with regard to production, extraction
and purification of the fatty acids. Several fatty acid products derived from fermentation of microorganisms are currently available commercially and are
being incorporated into some aqua-feeds. The microorganism fatty acids are
being used particularly in feeds destined for the rearing of the youngest developmental stages of fish and crustaceans (Bergé and Barnathan, 2005; Ward
and Singh, 2005; Guschina and Harwood, 2006; Spolaore et al., 2006).
Genetic modification of plants and animals by transgenesis gives rise to the
possibility of introducing unintentional side effects as a result of the insertion of
novel DNA into the genome. Possible results could be the increased biosynthesis
and accumulation of toxic metabolites, enhanced production of known or novel
Achievements and Challenges
15
allergenic proteins or reductions in tissue concentrations of certain essential
nutrients in the modified organism (Kok and Kuiper, 2003; Kuiper et al., 2004;
Liu-Stratton et al., 2004; Lehrer and Bannon, 2005; Rischer and OksmanCaldentey, 2006; Roy and Sen, 2006). Such changes could have negative
effects on an animal that consumes such products. Control measures have been
introduced in an attempt to reduce such risks and a number of methods, including metabolic profiling or metabolomics (the global mapping of metabolites
present within cells or tissues), are being developed to address these problems
(Kuiper et al., 2004; Liu-Stratton et al., 2004; Kato et al., 2005; Lehrer and
Bannon, 2005; Griffin, 2006; Rischer and Oksman-Caldentey, 2006; Müller
and Steinhart, 2007). Some of these methods have been applied to examination of the metabolic profiles of fish. These novel, modern methods have, however, been used mostly in toxicological studies to identify changes in metabolism
that result from the exposure of fish to toxicants or other forms of environmental stressor (e.g. Cakmak et al., 2006; Viant et al., 2006).
The assessment of the effects of including genetically modified feed ingredients in fish feeds is in its infancy and has mostly involved examination of
growth effects and histopathology (Brown et al., 2003; Glencross et al., 2003;
Hemre et al., 2005; Sanden et al., 2005, 2006); hitherto, no major negative
effects have been reported. Studies are also being conducted to examine the
degree to which dietary DNA is degraded in the gut and to what extent it is
taken up and distributed in body tissues; such studies are needed for assessment
of the potential for horizontal gene transfer from genetically modified feed
ingredients to the animal that consumes them (Sanden et al., 2004; Nielsen
et al., 2005, 2006).
1.5
Health Management and Disease Control
Infectious diseases are a major problem in all intensive animal production systems and intensive aquaculture is no exception; farm populations of aquatic
animals may be decimated by a disease outbreak, leading to serious losses of
production. Outbreaks of disease often occur when rearing conditions and animal welfare are poor, so a suboptimal environment is often a major contributory factor to such outbreaks. As such, health management starts with the
creation of a suitable rearing environment and continues with the maintenance
of that environment, including the minimizing of potential stressors (Håstein
et al., 2005; Keeling, 2005; Midtlyng, 2005; Murray and Peeler, 2005; Adams
and Thompson, 2006; Bricknell et al., 2006; Broom, 2006; Dawkins, 2006;
Huntingford et al., 2006; Lund, 2006; see Chapter 2, this volume).
The stock should be provided with water of good quality, sufficient space
and sufficient food of high nutritional quality and should also be subjected to
limited disturbance and physical handling. The difference between health and
disease depends on the balance between the pathogen and the host, and that
balance can be influenced greatly by environmental factors such as water
temperature and water quality (Bondad-Reantaso et al., 2005; Håstein et al.,
2005; Murray and Peeler, 2005; Huntingford et al., 2006). Biosecurity has
16
M. Jobling
disease prevention and prophylaxis as its key points. It involves implementation
of measures for prevention, control and eradication of economically important
diseases. In other words, biosecurity encompasses all procedures required to
protect the fish from contracting, carrying and spreading diseases and parasites
(Bondad-Reantaso et al., 2005; Midtlyng, 2005; Murray and Peeler, 2005).
A major source of disease-causing organisms for aquatic animals is the
water flowing into the rearing units, so treatment of incoming water is often
used to reduce the levels of waterborne pathogens to below infective limits (see
Chapter 2, this volume). Disinfection, which must inactivate a wide range of
bacteria, viruses and protozoans, may be accomplished by chemical or physical
means, such as chlorination, ozonation or treatment with UV or ionizing radiation. UV radiation treatment is frequently the method of choice for the disinfection of water to be used for aquaculture purposes (Lee, 2003; Sharrer et al.,
2005; Hijnen et al., 2006). An alternative, and not mutually exclusive alternative, to disinfection to combat disease-causing organisms involves the use of
probiotics. Probiotics may be defined as microorganisms that are administered
to the fish, either via the water or in the feed, and they then enter the gastrointestinal tract and serve a function in improving the health of the farmed stock
(Gatesoupe, 1999; Irianto and Austin, 2002; Balcázar et al., 2006; Vine
et al., 2006). The probiotics may act by stimulating the immune system of the
host fish, or they may have direct effects on potential pathogens. The direct
effects include interference with the metabolism of the pathogens via the production of inhibitory compounds by the probiotic microorganism and competition for nutrients or other resources (Gatesoupe, 1999; Irianto and Austin,
2002; Balcázar et al., 2006; Vine et al., 2006).
1.5.1
Diagnostics and disease treatment
Veterinary medicine has long traditions in health surveillance and disease diagnosis of terrestrial livestock, but incomplete knowledge about the environmental requirements and biology of farmed aquatic animals along with a relative
dearth of information about their diseases has meant that less has been achieved
to solve the medical problems faced by aquaculture stocks (Woo et al., 2002;
Storey, 2005; Bricknell et al., 2006). Molecular markers are being used for
diagnostic and epidemiological purposes in clinical and veterinary medicine
(Liu-Stratton et al., 2004; Monis et al., 2005; Adams and Thompson, 2006;
Chistiakov et al., 2006; Gasser, 2006) and DNA-based technologies are finding increased use in the production of vaccines and pharmaceutical agents with
human and animal health applications (Melamed et al., 2002; Houdebine,
2005; Midtlyng, 2005; Myhr and Dalmo, 2005; Dalal et al., 2006). As the
aquaculture industry continues to grow, these areas will probably increase in
priority as R & D objectives.
The development of diagnostic methods and vaccines against some of the
diseases that attack aquaculture species has been instrumental in preventing
disease outbreaks, thereby reducing the large-scale use of antibiotics and other
drugs for the treatment of certain diseases. Nevertheless, there are relatively
Achievements and Challenges
17
few commercial vaccines currently available and the pharmaceutical toolkit of
the aquaculture veterinarian is also limited (Midtlyng, 2005; Sommerset et al.,
2005; Storey, 2005; Bricknell et al., 2006; MacMillan et al., 2006).
1.5.1.1 Vaccines
Most vaccines are based on inactivated bacterial pathogens and few vaccines are
available for other disease organisms, such as viruses (Midtlyng, 2005; Rigos
and Troisi, 2005; Sommerset et al., 2005), although DNA vaccines against
some viral agents are under development (Melamed et al., 2002; Midtlyng,
2005; Myhr and Dalmo, 2005; Sommerset et al., 2005; Adams and Thompson,
2006). DNA vaccines are gene constructs that express cloned antigens transiently in the treated individual, thereby promoting the development of protection against the disease agent; R & D into DNA vaccines includes work on viral
haemorrhagic septicaemia, infectious haematopoetic necrosis, channel catfish
herpes virus, infectious salmon anaemia and infectious pancreatic necrosis.
Vaccines are usually administered by injection or by bath (immersion)
treatment. The former is labour-intensive and time-consuming if large numbers of animals are to be treated and bath treatments are often of reduced
efficacy compared with injection, so alternative methods of vaccine delivery
are being sought and developed (Vandenberg, 2004; Midtlyng, 2005; Adams
and Thompson, 2006). Oral administration of vaccine via the feed offers the
possibility of treating large numbers of animals with relative ease and avoids
the trauma associated with handling and the injection of vaccines, but the
efficacy of oral vaccination has, hitherto, proven variable (e.g. Esteve-Gassent
et al., 2004; Romalde et al., 2004; Vandenberg, 2004; Shoemaker et al.,
2006). Problems with oral vaccination relate to the possible degradation of
vaccine components in the digestive tract, requiring the development of microencapsulation, and other methods, for vaccine protection.
1.5.1.2
Antibiotics and other chemotherapeutic agents
At present, the vaccines available target diseases prevalent in a limited number
of farmed species, so the use of other disease treatments, such as antibiotics,
is widespread in the aquaculture industry (Rigos and Troisi, 2005; Bricknell
et al., 2006). Several antimicrobial agents, including tetracyclines, quinolones,
sulphonamides and amphenicols, may be efficacious for the treatment of bacterial diseases of aquatic animals, but the range of drugs, pharmaceutical and
other chemical agents approved for use in aquatic species is small compared
with the number of drugs licensed for use in terrestrial livestock (Storey, 2005;
MacMillan et al., 2006).
One major reason for this is that the size of the aquaculture market is currently too small to offer drug companies an adequate return on the economic
investment required to collect the documentation needed for approval to be
granted by licensing authorities; the requirements may include documentation
that the drug treatment is effective against the target disease in each specified
aquatic animal, that the drug is safe for the treated animal, does not pose a
hazard to humans who may consume the animal and does not give rise to
18
M. Jobling
environmental concerns (Midtlyng, 2005; Storey, 2005; MacMillan et al.,
2006). These requirements impose difficulties for the development and implementation of effective health management programmes for species that are
cultured in low volume or that are under consideration for commercial farming
(Storey, 2005; Bricknell et al., 2006). As the aquaculture industry expands,
the data needed for the licensing of pharmaceuticals are gradually being collected and are being made available to private companies and licensing authorities (Bondad-Reantaso et al., 2005; Reimschuessel et al., 2005; Rigos and
Troisi, 2005; Samuelsen, 2006).
Prophylactic use of vaccines and probiotics, combined with good management practices, reduces the incidence of disease outbreaks (Midtlyng, 2005;
Sommerset et al., 2005; Balcázar et al., 2006; Vine et al., 2006), which, in
turn, reduces the need to use antimicrobial drugs and chemotherapeutic agents
(Murray and Peeler, 2005; Rigos and Troisi, 2005). Reduced reliance on such
drug treatments has several benefits. For example, the treatment of water in
reuse culture systems usually relies on biological action to remove metabolic
wastes and the organisms responsible for the biodegradation of these wastes
will be susceptible to some of the agents used to combat disease organisms. In
this respect, the use of antibiotics, drugs and other chemical agents that kill
water-treatment microorganisms would act as a double-edged sword.
Further, there is public concern regarding the use of drugs and other
chemicals such as disinfectants, pesticides and chemotherapeutic agents in
aquaculture. The general public is concerned about possible environmental
contamination, and the negative effects that could result, and the possibility
that development of antibiotic resistance in aquatic microorganisms could be
transferred to human pathogens (Bondad-Reantaso et al., 2005; Focardi
et al., 2005; Rigos and Troisi, 2005; Adams and Thompson, 2006; MacMillan
et al., 2006; Toldrá and Reig, 2006). To help allay these concerns, the use of
medicated feeds should be kept to a minimum, every effort should be made to
prevent the loss of such feeds to the environment and all drugs, disinfectants
and other chemical agents must be used in a responsible manner (Boyd et al.,
2005; Focardi et al., 2005; Murray and Peeler, 2005; Rigos and Troisi, 2005;
Storey, 2005; MacMillan et al., 2006; Toldrá and Reig, 2006).
1.6 Food Products: Nutritional Composition,
Food Safety and Traceability
Aquaculture products intended as food should meet the tastes and expectations
of the consumer, but there are many factors that interact to influence the composition of these products. Most of these factors exert their influence prior to
harvest, but postharvest processing, transport and storage conditions can also
have a major influence. For example, the nature and nutrient composition of
the feed are directly influential in determining flesh characteristics, but other
agents, such as chemical therapeutic agents, drug residues and waterborne
pollutants and contaminants that impart off-flavours and taints to the flesh,
may also have direct effects (Fig. 1.4) (e.g. Tucker, 2000; Jobling, 2004a,b,c;
Achievements and Challenges
19
Fish characteristics
Species and stock (genetic selection)
Life cycle stage, sex and maturity
Health status (diseases and parasites)
Feeds and feeding
Feed composition (e.g. % fat, pigments)
Feed contaminants (e.g. aflatoxins, dioxins)
Feed amount and feeding frequency
Culture environment
Pollutants and contaminants (‘off-flavours’ and taints)
Temperature, salinity and light conditions
Water quality (e.g. oxygen, metabolic wastes)
Disease agents and parasites
Harvesting, processing,
transport and storage
Fig. 1.4. Summary of some of the major factors influencing flesh (fillet) composition of
farmed fish. The factors that play a role in determining the composition and ‘quality’ of the fish
that reach the market are the intrinsic (relating to the fish themselves) and extrinsic factors
(relating to feeds and feeding and the culture environment) that exert an influence during the
growth cycle and the postharvest changes that occur during processing and fish storage.
Bell et al., 2005; Berntssen et al., 2005; Carlson and Hites, 2005; Torstensen
et al., 2005; Bethune et al., 2006; Toldrá and Reig, 2006; see Chapters 2
and 3, this volume).
This means that attention must be given to food quality and safety at all
links in the food supply chain from the producer to the consumer. The establishment of clear objectives and accreditation procedures is integral to food
quality and safety management. Increased control over the safety and quality of
food is made possible by adopting agreed practices and implementing one or
more management systems, such as good manufacturing practice (GMP), good
hygiene practice (GHP) and hazard analysis critical control points (HACCP)
(Huss et al., 2004; Sumner et al., 2004; Boyd et al., 2005; Gorris, 2005;
da Cruz et al., 2006).
1.6.1
Analysis of aquaculture products
The versatility of NIR spectroscopy, and its advantages of speed and simplicity
of instrument operation, has resulted in its adoption as a rapid analytical tool
in many areas (Blanco and Villarroya, 2002; Reid et al., 2006), including the
seafood and aquaculture industries. The main application of NIR spectroscopy
within the seafood and aquaculture sectors has been for the prediction of
20
M. Jobling
chemical (nutritional) composition, but more recent applications include species identification and authentication, monitoring of degradation products for
assessment of freshness, spoilage and ‘quality’ and for discrimination between
fresh and frozen-thawed fish (Cozzolino et al., 2002, 2005,a,b; Nilsen et al.,
2002; Uddin and Okazaki, 2004; Nilsen and Esaiassen, 2005; Uddin et al.,
2005; Lin et al., 2006; Reid et al., 2006).
Alternatives to NIR spectroscopy are available for the assessment of spoilage via analysis of volatile compounds (e.g. aldehydes, ketones, organic acids
and their esters and ethers). The composition and concentration of volatile
compounds differs between fresh, stale and spoiled fish, with spoilage volatiles
developing as a result of oxidative or microbial degradation of the chemical
constituents of the tissues. Thus, as fish spoilage progresses, there is increased
production of basic volatile nitrogen compounds, such as trimethylamine,
ammonia and dimethylamine, and it is possible to detect changes in the concentrations of these spoilage compounds remotely (Pacquit et al., 2006). There
are also changes in other compounds as fish become spoiled, so there is a
change in the odour profile (aromagram) over time and these changes can be
used in quality assessment (Olafsdottir et al., 2004; Reid et al., 2006; Plutowska
and Wardencki, 2007).
Other methods for identifying the species and/or sources of seafood,
including aquaculture, products rely on molecular diagnostic techniques that
involve the detection of some form of biomarker. Several methods, such as
isoelectric focusing, electrophoresis and immunoassay, rely on the identification of specific proteins or groups of proteins for discrimination between species (Berrini et al., 2006), for identification of potential allergens (Lehrer et al.,
2003; Van Do et al., 2005; Kobayashi et al., 2006; Müller and Steinhart,
2007), or for detection of therapeutic agents and drug residues that may be
present in the products (Toldrá and Reig, 2006). For example, the major allergens present in seafood are muscle proteins – parvalbumins in fish and tropomysins in crustaceans – and immunoassays have been developed to detect the
allergens present in a range of seafood species (Lehrer et al., 2003; Van Do
et al., 2005; Kobayashi et al., 2006).
Other approaches to the rapid screening of food products for the
assurance of quality and safety are based on the use of DNA microarrays
(Liu-Stratton et al., 2004; Kato et al., 2005; Roy and Sen, 2006) and the
development of electronic sensors, biosensors or ‘biochips’ (Toldrá and Reig,
2006; Müller and Steinhart, 2007). A biosensor consists of a chemical recognition element or biological sensor, usually an antibody or enzyme, which is connected to a data processing unit. The target chemicals contact and bind to
specific biological sensors, the biomolecular interaction signals are converted
into electrical signals and the electrical signals are then processed by a microprocessor. Biochip array biosensors have the advantages that the method is
rapid and that food products can be screened for several chemicals simultaneously (as many as the number of specific recognition elements in the array), but
initial investment costs for the development of biosensors are quite high.
A variety of other biomarker-based methods has also been developed for
discrimination, authentication and quality evaluation purposes (Carbonaro,
Achievements and Challenges
21
2004; Bergé and Barnathan, 2005; Guérard et al., 2005; Kelly et al., 2005;
Pinotti et al., 2005; Reid et al., 2006; Renshaw et al., 2006; Toldrá and Reig,
2006; Müller and Steinhart, 2007). For example, techniques, such as PCRRFLP and PCR-RAPD, which rely on DNA markers, have advantages over
protein-based methods as they are less influenced by the tissue analysed, the
age of the individual and the effects of thermal degradation. Using DNA-marker
techniques, closely related species can be distinguished from each other and
these techniques may enable recognition of the species compositions of complex mixtures and processed products (Chistiakov et al., 2006). An additional
example is the use of fatty acid profiles for the discrimination of farmed from
wild fish; the fatty acids can be used as biomarkers because the fatty acid profiles of the animals generally reflect those of their food and the fatty acids
present in aqua-feeds will usually differ from those present in the natural prey
of the farmed species (e.g. Jobling, 2004a,b,c; Wonnacott et al., 2004; Bell
et al., 2005; Bergé and Barnathan, 2005; Berntssen et al., 2005; Torstensen
et al., 2005; Visentainer et al., 2005; see Chapter 3, this volume).
1.7 Fish as Food: Consumer Attitudes
(and the Question of GM-Fish)
Price, availability, taste, nutritional value, attitudes and moral considerations all
influence consumer food choice and there is increasing interest in food-related
issues among the public at large (Shanahan et al., 2001; Butterworth, 2004;
Huss et al., 2004; Bennett et al., 2005; Deisingh and Badrie, 2005; Frewer
et al., 2005; Gorris, 2005; Logar and Pollock, 2005; Toldrá and Reig, 2006;
Müller and Steinhart, 2007; see Chapters 22 and 26, this volume). There is
increasing media coverage of food-related topics but, for a variety of reasons,
media reporting may be incomplete or inaccurate (Butterworth, 2004; Logar
and Pollock, 2005; Bruhn and Earl, 2006). This gives cause for concern, especially as adverse messages or negative press related to food safety can have a
major influence on consumers’ purchasing decisions; unfavourable messages
weigh much more heavily in influencing consumer decisions than do positive or
favourable ones.
Recent examples of food-related topics covered in a negative light in newspapers, magazines and other media include ‘mad cow disease’ (BSE), use of
hormones in livestock production, pesticide and other xenobiotic residues in
foods, use of food additives (preservatives and colorants), the planting of GM
crops and the raising of GM animals for human consumption. Thus, markets
for fish and animal food products are frequently challenged with stories relating
to ‘health scares’. For example, although the nutritional value and potential
health benefits of eating fish are regularly stated and increased consumption of
fish is advised by nutritionists, many people appear to have a greater awareness of the safety risks that may be linked to fish consumption (Huss et al.,
2004; Verbeke et al., 2005). The latter seems to be the result of a greater
mass-media focus on pollution issues and contamination of fish than on communicating information about dietary recommendations and the potential
22
M. Jobling
health benefits of increased consumption of fish. Thus, fish and farm animal
producers need to identify clear, solidly documented ‘health benefit’ messages
that can be used to promote the marketing of fish and animal products and
offset the negative images created by ‘health scare’ propaganda.
In the mind of the general public, transgenic technology and GMOs seem
to be both food (nutritional) and animal welfare issues, although the link between
the two may be rather tenuous. Although there is currently no scientific evidence for any hazards unique to GMOs, there are consumer fears about food
safety, ecosystem disturbance and degradation and animal welfare (Beardmore
and Porter, 2003; Bennett et al., 2005):
●
●
●
Food safety: is consumption of GMOs safe or are there unknown dangers?
Environmental impacts: how might escapees influence natural populations
of conspecifics and/or other species?
Welfare and ethics: is it morally defensible to manipulate higher organisms
to the extent possible using modern biotechnological techniques?
There are probably many reasons for the lack of clarity around the issue of
GMOs, but one result of the confused state of affairs has been market resistance against such products (Tucker, 2003; Aerni, 2004; Kuiper et al., 2004;
Deisingh and Badrie, 2005; Lehrer and Bannon, 2005; Logar and Pollock,
2005; Myhr and Dalmo, 2005; Tenbült et al., 2005; Bruhn and Earl, 2006;
Dalal et al., 2006; Saher et al., 2006). In general, attitudes towards GMOs
and organically grown food (OGF) are negatively related (Bennett et al., 2005;
Dreezens et al., 2005; Saher et al., 2006). Strictly speaking, GMOs and OGFs
refer to different methods of production rather than to any distinct properties
or unique nutritional qualities of the end product. Nevertheless, consumers tend
to treat such products as being inherently different from each other and from
foods produced by conventional methods. The general public usually associates
OGFs with ‘naturalness and pureness’, whereas GMOs are seen as having been
altered extensively and manipulated by human hands, and this often results in
a negative attitude towards GM products.
Consumer acceptance of a GM product also appears to be influenced by
the way the generic product type is perceived; GM is less acceptable when a
product type is viewed as being ‘natural and healthy’, such as the case with
fruits and vegetables, than when the product is already seen as being ‘manufactured, unnatural and unhealthy’, as with cakes, biscuits and snack-foods (Tenbült
et al., 2005). The resistance to GMOs appears to be particularly widespread
with regard to farmed fish; this is not surprising, given that fish and fish products would normally be considered as falling within the category of ‘natural and
healthy’ foods. In other words, potential consumers often view GM farmed fish
as being contrary to the image of an ‘ecologically sound, natural, health food’
(Bennett et al., 2005; Logar and Pollock, 2005).
Given this, there is a need for caution and increased transparency associated with the regulation, licensing and broader introduction of such products,
and it is also essential that effective methods be developed for the detection of
GM products that enable them to be distinguished readily from non-GM entities
(Beardmore and Porter, 2003; Kok and Kuiper, 2003; Kuiper et al., 2004;
Achievements and Challenges
23
Liu-Stratton et al., 2004; Deisingh and Badrie, 2005; Kato et al., 2005;
Lehrer and Bannon, 2005; Myhr and Dalmo, 2005; Bruhn and Earl, 2006;
Roy and Sen, 2006; Stewart, 2006; Müller and Steinhart, 2007). For example, regulations need to include consideration of the safeties of the inserted
DNA and markers introduced to help in the identification of GMOs. There
must also be evaluation of the potential toxicity and allergenicity of the gene
products resulting from the introduction of novel DNA, and the possibility of
horizontal gene transfer also needs to be considered.
1.8
Concluding Remarks
There has been a rapid increase in aquaculture production over the course of the
past few decades (http://www.fao.org/figis) and many predict that this expansion will continue for several years to come. If the predictions are to come to fruition, several prerequisites must be fulfilled. Government agencies and public
authorities must create conditions that foster advances in aquaculture R & D.
They should also promote advisory services designed to serve the industry and
they must issue the regulations necessary for the maintenance of the trust and
confidence of the public. Research institutions currently have a range of modern
techniques available that enable them to provide results in genetics and selective
breeding, nutrition and aqua-feed development and management practices that
can lead to the production of quality aquaculture products at affordable cost. The
industry must be in a position to realize the potential of the research results in a
commercial setting and farmers must be receptive to, and apply, new techniques
that lead to improvements in the efficiency of their operations.
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