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DFO - Library

/ MPO Bibliothèque 1111

111111111111111111 II

C-CARC

12004349

II

National Research Conseil national

Council Canada de recherches Canada

MIM Canadian Special Publication of Fisheries and Aquatic Sciences 120

Risk Evaluation and

Biological Reference Points

for Fisheries Management

Edited by

Stephen J.

Smith, Joseph J. Hunt, and D. Rivard

20 40 60 80

Quantifiable Management Action

Department

o; Fisherîes & Oceans

DEC 20 lei

Ministère des Pèches et dcs

Océans

T T A nAl A

Canadian Special Publication of Fisheries and Aquatic Sciences 120

Risk Evaluation and Biological Reference Points

for Fisheries Management

Edited by

Stephen J.

Smith

Department of Fisheries and Oceans

Bedford Institute of Oceanography

P O. Box 1006

Dartmouth, Nova Scotia, Canada B2Y 4A2

Joseph J. Hunt

Department of Fisheries and Oceans

Biological Station

St. Andrews, New Brunswick, Canada EOG 2X1

Denis Rivard

Department of Fisheries and Oceans

Fisheries Research Branch 200

Kent Street, Stn. 1256

Ottawa, Ontario, Canada KlA 0E6

NATIONAL RESEARCH COUNCIL AND DEPARTMENT OF FISHERIES AND OCEANS

Ottawa 1993

C) National Research Council of Canada 1993

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted by any means, electronic, mechanical,

photocopying, recording or otherwise, without the prior written permission of the National Research Council of Canada, Ottawa, Canada K I A 0R6.

ISBN 0-660-14956-7

ISSN 0706-6481

NRCC No. 36178

Canadian Cataloguing In Publication Data

Main entry under title:

Risk evaluation and biological reference points for fisheries management (Canadian special publication of fisheries and aquatic sciences; ISSN 0706-6481; no. 120) Includes an abstract in French. Includes bibliographical references. This volume contains 31 peer reviewed papers presented at the workshop held on November 19-22,

1991, in Halifax, Nova Scotia. - Abst.

ISBN 0-660-14956-7

1. Fishery management - Canada - Congresses. 2. Fisheries - Canada - Congresses.

I. Sinith, Stephen J. II. Hunt, Joseph J. III. Rivard, Denis. IV. National Research Council Canada. V. Canada, Dept. of Fisheries and Oceans. VI. Series.

SH328.R57 1993 333.95'6'0971 C93-099680-1

This publication is available from:

Subscription Office, Research Journals, National Research Council of Canada, Building M-55, Montreal Road, Ottawa, Ontario, Canada K IA 0R6

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Printed on recycled paper.

Correct citation for this publication:

SMITH, S. J., J. J. HUNT, AND D. RIVARD. 1993. Risk evaluation and biological reference points for fisheries management. Can. Spec. Publ. Fish. Aquat. Sci.

120: viii + 442p.

Table of Contents

Abstract/Résumé

Introduction vi

Biological reference points - some opening comments. J. B. Morrissey 1

Working Group Reports 5

Session I: Biological Reference Points

Reference points for fisheries management: the western Canadian experience. B. M. Leaman 15

Reference points for fisheries management: the eastern Canadian experience. D. Rivard and J.-J. Maguire 31

Reference points for fisheries management: the ICES experience. M. Hildén 59

Spawning stock biomass per recruit in fisheries management: foundation and current use. C. P. Goodyear 67

The development of a management procedure for the South African anchovy resource. D. S. Butterworth and

M. O. Bergh 83

How much spawning per recruit is enough? P. M. Mace and M. P. Sissenwine 101

The behaviour of Flow, Frned and Piligh in response to variation in parameters used for their estimation. T. Jakobsen . . 119

The Barents Sea capelin stock collapse: a lesson to learn. S. Tjelmeland and B. Bogstad 127 Session II: Identifying and Quantifying Uncertainties

Assessing the impact of sampling error on model-based management advice: comparison of equilibrium yield per recruit

variance estimators (Abstract). D. Pelletier and P. Gros 143

Variance estimates for fisheries assessment: their importance and how best to evaluate them. A. E. Punt and

D. S. Butterworth 145

Evaluating the accuracy of projected catch estimates from sequential population analysis and trawl survey abundance

estimates. S. J. Smith and S. Gavaris 163

Bootstrap estimates of ADAPT parameters, their projection in risk analysis and their retrospective patterns.

R. K. Mohn 173

Analytical estimates of reliability for the projected yield from commercial fisheries. S. Gavaris 185

Risk evaluation of the 10% harvest rate procedure for capelin in NAFO Division 3L. P. A. Shelton, J. E. Carscadden and

J. M. Hoenig 193

Using jackknife and Monte Carlo simulation techniques to evaluate forecast models for Atlantic salmon (Salmo salar).

R. R. Claytor, G. A. Nielson and P. A. Shelton 203

Monte Carlo evaluation of risks for biological reference points used in New Zealand fishery assessments.

R. I. C. C. Francis 221

A comparison of event tree risk analysis to Ricker spawner-recruit simulation: an example with Atlantic menhaden.

D. S. Vaughan

231

Choosing a management strategy for stock rebuilding when control is uncertain. A. A. Rosenberg and S. Brault 243

Session III: Alternative Strategies and Reference Points

Risks and uncertainties in the management of a single-cohort squid fishery: the Falkland Islands Illex fishery as an

example. M. Basson and J. R. Beddington 253 Risks of over- and under-fishing new resources. A. D. M. Smith 261

Estimation of density-dependent natural mortality in British Columbia herring stocks through SSPA and its impact on

sustainable harvesting strategies. V. Haist and D. A. Fournier 269

The comparative performance of production-model and ad hoc tuned VPA based feedback-control management procedures

for the stock of Cape hake off the west coast of South Africa. A. E. Punt 283 Groundfish exploitation rates based on life history parameters (Abstract). W. G. Clark 301 A proposal for a threshold stock size and maximum fishing mortality rate. G. G. Thompson 303 Biological reference points for Canadian Atlantic gadoid stocks. J.-J. Maguire and P. M. Mace 321 Stochastic locally-optimal harvesting. Joseph Horwood 333

ITQ based fisheries management. R. Arnason 345

Bioeconomic methods for determining TAC's. H. P. Palsson, D. E. Lane and B. Kaufmann 357 Management strategies: Fixed or variable catch quotas. S. I. Steinshamn 373

Bioeconomic impacts of TAC adjustment strategies: a model applied to northern cod. D. E. Lane and B. Kaufmann . 387

Experimental management programs for two rockfish

stocks off British Columbia, Canada. B. M. Leaman and

R. D. Stanley

403

A brief overview of the experimental approach to reducing uncertainty in fisheries management - an extended abstract.

R. M. Peterman and M. K. McAllister

419
Fisheries management organizations: a study of uncertainty. R. O'Boyle 423

Appendix A: List of Participants

437

Appendix B: Workshop Schedule 438

Appendix C: Referee List

442
iv

Abstract/Résumé

Smith, S. J., J. J. Hunt and D. Rivard. 1993. Risk evaluation and biological reference points for fisheries management.

Can. Spec. Publ. Fish. Aquat. Sci. 120.

The Canadian Atlantic Fisheries Scientific Advisory Committee (CAFSAC) of the Canadian Department of Fisheries

and Oceans sponsored a workshop on Risk Evaluation and Biological Reference Points for Fisheries Management,

November 19-22, 1991, in Halifax, Nova Scotia. This meeting was attended by 60 fisheries scientists and economists

fronn Australia, Canada, Finland, France, Iceland, New Zealand, Norway, South Africa, the United Kingdom and the

United States. This volume contains 31 papers presented at the workshop in three theme sessions. In the first

session the use, track record, strengths and weaknesses of commonly used biological reference points (e.g., Frned,

F0.1, SSB/R) were reviewed. Papers in the second session were focussed on methods for identifying and quantifying

the uncertainties associated with using various reference points. Alternative management strategies based on new

reference points or suggested strategies for dealing with novel situations (e.g. developing new fisheries resources,

management of stock complexes) were the subject of the third session. This volume also includes the reports of

four working groups formed to answer specific questions on the application of risk evaluation and biological reference

points. These answers were presented by each group in plenary session at the end of the meeting. One common

thread which ran through all of the working groups presentations was the emphasis on the scientists' responsibility to

evaluate the different management strategies and the managers' responsibility to establish the objectives to be met by

these strategies. Du 19 au 22 novembre 1991, le Comité Scientifique Consultatif des Pêches Canadiennes dans l'A tlantique (CSCPCA), ministère Canadien des Pêches et Océans, a tenu à Halifax, N ouvelle Écosse, un atelier intitulé "Évaluation des risques et points de référence biologiques en gestion des pêche s». Soixante chercheurs et économistes du domaine des pêches, en provenance d'Australie, du Canada, de la Finlande, de la France, de LIslande, de la Nouvelle Zélande, de la Norvège, de l'Afrique du Sud, du Royaume-Uni et des États-Un is, y ont participé. Ce document renferme 31 articles présentés au cours de trois sessions thématiques. La p remière session a servi à faire le point sur l'utilisation, la performance, les forces et les faiblesses des points de référence biologiques d'usage général (e.g., Fmed, F0.1, BSR/R). Les articles présentés au cours de la deuxième session ont touc hé au méthodes d'identification et d'estimation des incertitudes associées à l'utilisation de divers points de réfé rence. Les stratégies de gestions fondées sur de nouveaux points de référence ainsi que des suggestions pour faire face à de nouvelles situations (e.g., développement de

nouvelles ressources halieutiques, gestion de complexes de stocks) ont fait l'objet de la troisième session. Ce document

contient également le rapport des quatre groupes formés afin d'adr esser des questions spécifiques sur l'application de l'évaluation des risques et de points de référence biologiques. Les réponses apportées ont été présentées par chaque groupe en session plénière à la fin de l'atelier. Tous les grou pes ont soulevé que, bien qu'il en est de la responsabilité

des chercheurs d'évaluer les différentes stratégies de gestion, l'établissement des objectif

s à rencontrer au moyen de ces stratégies doit être fait par les gestionnaires.

Introduction

T his volume contains the proceedings from the Work- shop on "Risk Evaluation and Biological Reference Points for Fisheries Management" which was held on Nov. 19-22, 1991 in Halifax, Nova Scotia. The Canadian Atlantic Fisheries Scientific Advisory Committee (CAFSAC) of the Government of Canada sponsored the meeting which was attended by 60 fisheries scientists and economists from Australia, Canada, Finland, France, Iceland, New Zealand, Norway, South Africa, the United Kingdom and the United

States (Appendix A).

One of the driving motivations for holding this workshop was to canvass fisheries scientists throughout the world on ways and means of dealing with all of the uncertainties inher- ent in managing a fishery. The fact that there are uncertain- ties associated with decision-making in fisheries management does not malce this process any different from most of the other decision-making processes in society. Nor is this the first time such uncertainties have been looked at in a fisheries science forum (see for e.g., Shepherd 1991). However, over the last few years there has been a great deal of interest in quantify- ing and incorporating the basic sources of uncertainties into fisheries management advice from CAFSAC. This interest is based on the assumption that we would present more useful and realistic advice if the uncertainties were recognized. The processes by which the uncertainties would be characterized and incorporated into fisheries advice were loosely termed 'risk' evaluation for the purposes of the workshop. A review of the many biological reference points currently in use (e.g. F0.1, _,

F.ned,

%SPR) was also seen to be timely. Im- pressive fisheries databases have accumulated over the past

15-20 years. Stock assessment methods have also evolved

and advances have been made in quantifying uncertainties in key parameters. Different management approaches have been adopted around the world to suit different realities; thus, an opportunity existed to compare different experiences and in- vestigate alternative approaches. An evaluation of the various reference points was of particular interest in eastern Canada where the groundfish industry had moved from an annual to a multi-year management plan. The workshop was designed to focus attention on "Bio- logical Reference Points" and "Risk Evaluation" in two ways. The first consisted of the presentation of 38 invited and con- tributed scientific papers in three sessions (Appendix B). In the first session the use, track record, strengths and weaknesses of biological reference points were reviewed. Au- thors of papers in this session were asked to comment on the role that uncertainties may have played in the successes or failures associated with the use of particular biological refer- ence points. One of the major sources of uncertainty common to many of the papers was not one of those usually identified as being important (variability in recruitment, aging errors, etc.). This major source of uncertainty identified was associ- ated with the lack of hard objectives for the management of fish stocks. Many authors pointed out the lack of well-defined social, economic or political objectives often resulted in bi- ological targets being assumed for the fishery. However, if the advice based upon the biological reference point(s) indi- cated severe conditions for the fishery, other objectives such as maintaining catch levels, reaching agreements amongst mem- ber nations in a multinational fishery, etc., became much more important. As a result, there was a general crie-de-coeur for an internationally accepted "biological" bottom line for stock depletion which would override any economic, social or po- litical objectives. Proponents of Spawning Stock Biomass per Recruit (SSB/R) based reference points have used recruit- ment overfishing as this bottom line and define the overfishing threshold as being between 20-30% of SSB/R when F = 0 depending upon taxonomic group. Methods for identifying and quantifying the uncertainties associated with using various reference points were the focus of the second session. The papers in this session fell into two categories. The first category comprised propagati on-of- error studies in which measured or assumed uncertainties in the basic data or model assumptions were carried through to estimates of the common quantities from assessment models (e.g., projected catch, yield-per-recruit). Bootstrap or Monte- Carlo techniques were used to study the propagation-of-error due to the complexity of the assessment models being stud- ied. We very quickly ran into a nomenclature problem with the variety of bootstrap and Monte-Carlo methods used, and in Table 1 we offer a key to the definitions of the different kinds of simulation methods used herein. The second category of papers in this session concentrated on simulation types of approaches to characterize the effects of the uncertainties in terms of the probability or "risk" of some consequence occurring (i.e. meeting a target, exceeding a set fishing mortality, etc.). The key thing to be determined in all such studies was what end event or consequence were we interested in - specifically, what event is 'risky' in the con- text of fisheries management. In many of the papers the end events were defined in terms of detrimental effects while two papers evaluated properties of the estimates used for man- agement advice. The paper by Rosenberg and Brault was unique in that it was not concerned with the standard sources of uncertainties (e.g., recruitment, M) but with the uncertain- ties associated with the ability of management to achieve a particular harvest rate in any one year. The presentations in the third session were concerned with alternative management strategies based on new reference vi

Pelletier and Gros

1991; Punt and Butter-

worth (this volume);

Smith and Gavaris (this

volume).

Punt and Butterworth

(this volume); Smith and Gavaris (this volume).

Mohn (this volume). Table

1. Definition of bootstrap methods used in the workshop.

Method

Model Assumptions

Form Definition Examples

Unconditional

Conditional'

Nonparametric Observed data are resampled with replacement to form new sets of data which are then used in subsequent analyses. This is the standard bootstrap of Efronquotesdbs_dbs29.pdfusesText_35

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