Dynamics of Pelagic Fish Distribution and Behaviour: Effects on Fisheries and Stock Assessment Pierre Freon ORSTOM, BP 5045, 3402 Montpellier, France OIe Arve Misund [MR, PO Box 1870, N-5024 Bergen, Norway Fishing News Books Copyright © 1999 DISTRIBUTORS Marston Book Services Ltd Fishing News Books PO Box 269 A division of Blackwell Science Ltd Abingdon Editorial Offices: Oxon OXI4 4YN Osney Mead, Oxford OX2 OEL (Orders: Tel: 01865206206 25 John Street, London WCIN 2BL Fax: 01865721205 23 Ainslie Place, Edinburgh EH3 6AJ Telex: 83355 MEDBOK G) 350 Main Street, Maiden MA 021485018, USA USA 54 University Street, Carlton Blackwell Science, Inc. 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No part of this publication may be reproduced, stored in a retrieval system, or A catalogue record for this title is available transmitted, in any form or by any means, from the British Library electronic, mechanical, photocopying, recording or ISBN 0-85238-241-3 otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. For further information on Fishing News Books, visit our website: First published 1999 http://www.blacksci.co.ukjfnbj Set in IOjl2.5pt Times by DP Photosetting, Aylesbury, Bucks Printed and bound in Great Britain at the University Press, Cambridge Contents Foreword ix Prej"ace xi 1 Introduction 1 1.1 Recent history of animal behaviour studies and focus on fish behaviour· 1 1.2 Brief history of stock assessment methods 5 1.3 Scope of the book 8 2 Pelagic Fisberies 10 2.1 World catch of small pelagic species 10 2.2 World catch of large 'mackerel and tuna 14 2.3 Fishing methods for pelagic species 15 2.3.1 Purse seining 15 2.3.2 Midwater trawling 18 2.3.3 Line fishing 19 2.4 Summary 20 3 Habitat Selection and Migration 21 3.1 Introduction 21 3.2 Habitat selection according to different time and space scales 22 3.3 Influence of abiotic (physical) factors 27 3.3.1 Temperature 28 3.3.2 Salinity 32 3.3.3 Dissolved oxygen 33 3.3.4 Water transparency 36 3.3.5 Light intensity 36 3.3.6 Current, turbulence and upwelling 38 3.3.7 Depth of the fish in the water column 40 3.3.8 Bottom depth and the nature of the sea bed 41 3.3.9 Floating objects 44 3.4 Influence of biotic factors 44 3.4.1 Conspecifics and the ideal free distribution 44 3.4.2 Other species 48 3.4.3 Prey 48 3.4.4 Predators 52 3.5 Conclusion 54 IV Contents 4 Schooling Behaviour 56 4.1 Introduction 56 4.2 School definitions 56 4.3 Genetic basis of schooling 57 4.4 Ontogeny of schooling 58 4.5 Schooling and shoaling 59 4.6 Functions of schooling 60 4.6.1 Surviving predatory attack 60 4.6.2 Effective feeding 63 4.6.3 Hydrodynamic advantages 63 4.6.4 Migration 64 4.6.5 Reproduction 64 4.6.6 Learning 65 4.7 School size 65 4.8 School organisation 68 4.8.1 Study methods 68 4.8.2 Minimum approach distance 70 4.8.3 Nearest neighbour distance 71 4.8.4 Spatial distribution 72 4.8.5 Internal synchrony 75 4.8.6 Individual preferences and differences 77 4.8.7 Packing density 78 4.8.8 Packing density structure 79 4.8.9 School shape 80 4.8.10 Factors affecting school structure 82 4.8.11 Factors selecting for homogeneity, structure and synchrony 86 4.9 Mixed-species schools. 88 4.10 Spatial distribution (clustering) 93 4.11 Communication 94 4.11.1 Vision 95 4.11.2 Lateralline 97 4.11.3 Hearing 98 4.12 Schooling, modern fishing and natural selection 98 4.13 Conclusion 100 5 Avoidance 102 5.1 Avoidance of sounds from vessel and gear 102 5.1.1 Ambient noise in the sea 102 5.1.2 Noise from vessels 103 5.1.3 Fish hearing 108 5.1.4 Fish reactions to noise 116 5.2 Visually elicited avoidance 122 5.2.1 Light in the sea 122 5.2.2 Fish vision 123 Contents v 5.2.3 Avoidance reactions elicited by visual stimuli of vessel and gear 124 5.3 Conclusion 126 6 Attraction and Association 128 6.1 Attraction to light 128 6.2 Attraction to bait 131 6.3 Associative behaviour 133 6.3.1 Association with floating objects 133 6.3.2 Association with other species 154 6.3.3 Summary of associative behaviour 157 7 Learning 159 7.1 Introduction 159 7.2 Learning in fish predation 159 7.2.1 Individuallevel 160 7.2.2 Interactions at the group level 163 7.2.3 Interactions among the prey 164 7.2.4 Key stimuli in learning 164 7.2.5 Hypothesis on interactive learning 167 7.2.6 From natural predators to fishing gear 167 7.3 Other learning processes 171 7.4 Conclusion 173 8 Effects of Behaviour on Fisheriesand Stock Assessment using Population Dynamic Models 174 8.1 Introduction 174 8.2 Stock assessment by population dynamic models 174 8.2.1 Stock assessment by surplus-production models 174 8.2.2 Stock assessment by age-structured models and yield per recruit 179 8.2.3 Stock-recruitment relationship 182 8.3 Habitat selection and its influence on catchability and population parameters 183 8.3.1 Yearly changes in abundance, density, habitat and catchability in relation to exploitation and the environment 183 8.3.2 Some attempts at modelling the yearly variability of catchability in relation to habitat selection 193 8.3.3 Seasonal variability of catchability in relation to habitat selection 200 8.3.4 Circadian variation of catchability related to habitat selection 204 8.3.5 Spatial variability of catchability in relation to habitat selection 208 VI Contents 8.3.6 Influence of habitat selection on growth estimate 214 8.3.7 Influence of habitat selection on mortality estimate by ASA models 214 8.4 Influence of aggregation on fisheries and population dynamic models 215 8A.I Influence of aggregation on catchability 215 8.4.2 Influence of mixed-species schools on abundance indices 230 8.4.3 Influence of aggregation on growth estimates and age-length key 232 8.5 Influence of avoidance on abundance indices 235 8.6 Influence of attraction and associative behaviour on population modelling 236 8.6.1 Influence of attraction 236 8.6.2 Influence of association 236 8.7 Influence of learning on-stock assessment 239 8.7.1 Influence of learning on surplus-production models 240 8.7.2 Influence of learning on intraspecific diversity and stock identification 244 8.7.3 Influence of learning on structural models 247 8.7.4 The strength of paradigms 248 8.8 Conclusion 249 9 Effects' of Behaviour on Stock Assessment using Acoustic Surveys 251 9.1 Introduction 251 9.2 The hydroacoustic assessment method 251 9.3 Effects of habitat selection 252 9.4 Effects of social behaviour 254 9.4.1 Distribution function of densities 254 9.4.2 Target strength 254 9.4.3 Acoustic shadowing 256 9.5 Effects ofavoidance 258 9.5.1 Methods to study vessel avoidance 258 9.5.2 Observations of vessel avoidance during surveys 260 9.5.3 Avoidance of vessel light 266 9.5.4 Vessel avoidance during sampling by trawls 267 9.5.5 Instrument avoidance 269 9.5.6 Sampling gear avoidance 270 9.6 Replicability of acoustic survey estimates 271 9.7 Conclusion 272 10 Other Methods of Stock Assessment and Fish Behaviour 274 10.1 Fishing gear surveys 274 10.1.1 Methodology and assumptions 274 10.1.2 Influence of fish behaviour on fishing gear surveys 275 10.2 Aerial surveys 276 10.2.1 Methodology and assumptions 276 Contents vii 10.2.2 Influence of fish behaviour on aerial survey 277 10.3 Ichthyoplankton surveys 279 10.3.1 Objectives, methodology and assumptions 279 10.3.2 Influence of fish behaviour on ichthyoplankton surveys 281 10.4 Capture-recapture 282 10.4.1 Methodology and assuptions 282 10.4.2 Influence of fish behaviour on capture-recapture methods 283 10.5 Conclusion 284 11 Conclusion 285 References 290 Index 339 Foreword By Alain Laurec and Anne E. M agurran The arrival of this book is timely. A split has occurred in fisheries research, between those population dynamicians who use only indirect methods derived from cohort analysis and those who prefer direct assessment. Freon and Misund show how this division is unnecessary, and how behavioural techniques can put a different light on the study of fisheries resources. The authors are wellqualified to establish such a link between the two camps. Their individual experience is complementary, particularly at the geographical level where their knowledge covers a wide area from tropical to Arctic seas and includes fresh water, pelagic coastal fish, and large migratory species.