Consequences of fish behaviour for stock assessment (original) (raw)

Dynamics of pelagic fish distribution and behaviour : effects on fisheries and stock assessment

Fishing News eBooks, 1999

Contents 4 Schooling Behaviour 4.1 Introduction 4.2 School definitions 4.3 Genetic basis of schooling 4.4 Ontogeny of schooling 4.5 Schooling and shoaling 4.6 Functions of schooling 4.6.1 Surviving predatory attack 4.6.2 Effective feeding 4.6.3 Hydrodynamic advantages 4.6.4 Migration 4.6.5 Reproduction 4.6.6 Learning 4.7 School size 4.8 School organisation 4.8.1 Study methods 4.8.2 Minimum approach distance 4.8.3 Nearest neighbour distance 4.8.4 Spatial distribution 4.8.5 Internal synchrony 4.8.6 Individual preferences and differences 4.8.7 Packing density 4.8.8 Packing density structure 4.8.9 School shape 4.8.10 Factors affecting school structure 4.8.11 Factors selecting for homogeneity, structure and synchrony 4.9 Mixed-species schools. 4.10 Spatial distribution (clustering) 4.11 Communication 4.11.1 Vision 4.11.2 Lateralline 4.11.3 Hearing 4.12 Schooling, modern fishing and natural selection 4.13 Conclusion 5 Avoidance 5.1 Avoidance of sounds from vessel and gear 5.1.1 Ambient noise in the sea 5.1.2 Noise from vessels 5.1.3 Fish hearing 5.1.4 Fish reactions to noise 5.2 Visually elicited avoidance 5.2.1 Light in the sea 5.2.2 Fish vision 88 100 102 102 102 103 108 116 122 122 123 Contents v 5.2.3 Avoidance reactions elicited by visual stimuli of vessel and gear 5.3 Conclusion 6 Attraction and Association 128 6.1 Attraction to light 6.2 Attraction to bait 131 6.3 Associative behaviour 6.3.1 Association with floating objects 6.3.2 Association with other species 6.3.3 Summary of associative behaviour 7 Learning 159 7.1 Introduction 7.2 Learning in fish predation 7.2.1 Individuallevel 7.2.2 Interactions at the group level 7.2.3 Interactions among the prey 7.2.4 Key stimuli in learning 7.2.5 Hypothesis on interactive learning 7.2.6 From natural predators to fishing gear 7.3 Other learning processes 171 7.4 Conclusion 8 Effects of Behaviour on Fisheries and Stock Assessment using Population Dynamic Models 174 8.1 Introduction 8.2 Stock assessment by population dynamic models 8.2.1 Stock assessment by surplus-production models 8.2.2 Stock assessment by age-structured models and yield per recruit 8.2.3 Stock-recruitment relationship 8.3 Habitat selection and its influence on catchability and population parameters 8.3.1 Yearly changes in abundance, density, habitat and catchability in relation to exploitation and the environment 8.3.2 Some attempts at modelling the yearly variability of catchability in relation to habitat selection 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 8.3.7 Influence of habitat selection on mortality estimate by ASA models 8.4 Influence of aggregation on fisheries and population dynamic models 8A.I Influence of aggregation on catchability 8.4.2 Influence of mixed-species schools on abundance indices 8.4.3 Influence of aggregation on growth estimates and age-length key 8.5 Influence of avoidance on abundance indices 8.6 Influence of attraction and associative behaviour on population modelling 8.6.1 Influence of attraction 8.6.2 Influence of association 8.7 Influence of learning on-stock assessment 8.7.1 Influence of learning on surplus-production models 8.7.2 Influence of learning on intraspecific diversity and stock identification 8.7.3 Influence of learning on structural models 8.7.4 The strength of paradigms 8.8 Conclusion 9 Effects' of Behaviour on Stock Assessment using Acoustic Surveys 9.1 Introduction 9.2 The hydroacoustic assessment method 9.3 Effects of habitat selection 9.4 Effects of social behaviour 9.4.1 Distribution function of densities 9.4.2 Target strength 9.4.3 Acoustic shadowing 9.5 Effects ofavoidance 9.5.1 Methods to study vessel avoidance 9.5.2 Observations of vessel avoidance during surveys 9.5.3 Avoidance of vessel light 9.5.4 Vessel avoidance during sampling by trawls 9.5.5 Instrument avoidance 9.5.6 Sampling gear avoidance 9.6 Replicability of acoustic survey estimates 9.7 Conclusion 10 Other Methods of Stock Assessment and Fish Behaviour 10.1 Fishing gear surveys 10.1.1 Methodology and assumptions 10.1.2 Influence of fish behaviour on fishing gear surveys 10.2 Aerial surveys 10.2.1 Methodology and assumptions Contents vii 10.2.2 Influence of fish behaviour on aerial survey 10.3 Ichthyoplankton surveys 10.3.1 Objectives, methodology and assumptions 10.3.2 Influence of fish behaviour on ichthyoplankton surveys 10.4 Capture-recapture 10.4.1 Methodology and assuptions 10.4.2 Influence of fish behaviour on capture-recapture methods 10.5 Conclusion 11 Conclusion References Index XII Preface We are grateful to several people for helping us in developing this book. The first scientific content was discussed by the authors with Francois Gerlotto, who is warmly acknowledged for his input and for the revision of some chapters. The preparation of the book was made possible through a 6 month employee contract from ORSTOM, France, to Ole Arve Misund in 1992, and a guest scientist scholarship for 2 months from the Norwegian Research Council to Pierre Freon in 1993. We are also grateful to many colleagues who took time to revise several chapters and to provide useful comments. Among them we extend special thanks to P. Cayre, A. Fonteneau and F. Marsac. Additional comments were provided by D. Binet, F.

The Assessment of the Exploitable Fish Reserves (Stock Assessment)

Progressive Engineering Practices in Marine Resource Management

This chapter explains some theoretical and technical aspects of stock assessments that may be familiar to those directly involved in fisheries science and analysis of fish populations. The information about stock and recruitment concepts, assessment of population growth, natural and fishing moralities, selectivity of fishing gears and relationship between catch and selectivity. It is written particularly for persons involved in scientific activity, for students and for stakeholders who have never been exposed to formal fisheries science training, but are interested in better understanding complicated fisheries concepts. An enhanced knowledge of assessment concepts and fisheries science will promote an increased understanding of fisheries management and give stakeholders greater confidence as they participate in fisheries management process. Understanding how all factors interact is a challenging task, even for experts in fisheries science.

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W. Ligtvoet, O.C. Mkumbo, P.J. Mous & P.C. Goudswaard In this chapter a detailed account is given of the suitability of various gear types for obtaining data, collected by researchers working independently of the fishery, on stock size, stock structure, growth, mortalitity, spatial and seasonal patterns, reproduction, condition and diet of the commercially important fish species of Lake Victoria, Nile perch (Lates), dagaa {Rastrineobola argentea) and Nile tilapia (Oreochromis niloticus).

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Basic objective of fisheries research is to provide ample information on the status of fish stocks. This information is collected through various sampling procedures and the data are used to provide advice on the sustainable management of fish stocks, upon which the entire fishing industry depends. There are two main sources of data collected and used in fisheries research. These can be divided into fishery independent and fishery dependent data. The first usually involves monitoring the changes in distribution over time in the relative or absolute abundance of fish populations using vessel based surveys in a way that is not subject to the biases inherent in commercial fishery data. The collection and accurate interpretation of both fishery dependent and fishery independent data are of fundamental importance to our understanding of the fished species. Both are needed to gain an understanding of the magnitude of localized changes in fish communities, landings and productivity of the ...

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