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IMPROVING FISH STOCK ASSESSMENTS

Committee on Fish Stock Assessment Methods

Ocean Studies Board

Commission on Geosciences, Environment, and Resources

National Research Council

NATIONAL ACADEMY PRESS
Washington, D.C.
1998



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--> IMPROVING FISH STOCK ASSESSMENTS Committee on Fish Stock Assessment Methods Ocean Studies Board Commission on Geosciences, Environment, and Resources National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1998

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--> NATIONAL ACADEMY PRESS 2101 Constitution Avenue, N.W. Washington, D.C. 20418 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competencies and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility of advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. William A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce M. Alberts and Dr. William A. Wulf are chairman and vice chairman, respectively, of the National Research Council. This report and the committee were supported by the National Oceanic and Atmospheric Administration. The views expressed herein are those of the authors and do not necessarily reflect the views of the sponsor. This study was supported by Contract No. 50-DGNC-3-00016 between the National Academy of Sciences and the National Oceanic and Atmospheric Administration. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the organizations or agencies that provided support for the project. Library of Congress Catalog Card Number 98-84433 International Standard Book Number 0-309-05725-6 Additional copies of this report are available from: National Academy Press 2101 Constitution Ave., NW Box 285 Washington, D.C. 20055 800-624-6242 202-334-3313 (in the Washington metropolitan area) http://www.nap.edu Copyright 1998 by the National Academy of Sciences. All rights reserved. Printed in the United States of America.

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--> Committee on Fish Stock Assessment Methods RICHARD DERISO (Cochairman), Inter-American Tropical Tuna Commission, La Jolla, California TERRANCE QUINN (Cochairman), University of Alaska Fairbanks, Juneau JEREMY COLLIE, University of Rhode Island, Narragansett RAY HILBORN, University of Washington, Seattle CYNTHIA JONES, Old Dominion University, Norfolk, Virginia BRUCE LINDSAY, Pennsylvania State University, University Park ANA PARMA, International Pacific Halibut Commission, Seattle, Washington SAUL SAILA, University of Rhode Island, Narragansett LYNDA SHAPIRO, University of Oregon, Charleston STEPHEN JOSEPH SMITH, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada CARL WALTERS, University of British Columbia, Vancouver, Canada Staff EDWARD R. URBAN, JR., Study Director LORA TAYLOR, Senior Project Assistant

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--> Ocean Studies Board KENNETH BRINK (Chairman), Woods Hole Oceanographic Institution, Massachusetts ALICE ALLDREDGE, University of California, Santa Barbara DAVID BRADLEY, Pennsylvania State University, State College WILLIAM CURRY, Woods Hole Oceanographic Institution, Massachusetts ELLEN DRUFFEL, University of California, Irvine RANA FINE, University of Miami, Florida CARL FRIEHE, University of California, Irvine ROBERT GAGOSIAN, Woods Hole Oceanographic Institution, Massachusetts SUSAN HANNA, Oregon State University, Corvallis JOHN HOBBIE, Marine Biological Laboratory, Woods Hole, Massachusetts EILEEN HOFMANN, Old Dominion University, Norfolk, Virginia JOHN KNAUSS, University of Rhode Island, Narragansett ROBERT KNOX, University of California, San Diego RAY KRONE, University of California, Davis LOUIS LANZEROTTI, Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey JOHN MAGNUSON, University of Wisconsin, Madison WILLIAM MERRELL, The H. John Heinz III Center for Science, Economics and the Environment, Washington, D.C. B. GREGORY MITCHELL, University of California, San Diego NEIL OPDYKE, University of Florida, Gainesville MICHAEL ORBACH, Duke University Marine Laboratory, Beaufort, North Carolina TERRANCE QUINN, University of Alaska Fairbanks, Juneau C. BARRY RALEIGH, University of Hawaii, Honolulu JAMES RAY, Shell Oil Company, Houston, Texas GEORGE SOMERO, Stanford University, Pacific Grove, California PAUL STOFFA, University of Texas, Austin Staff MORGAN GOPNIK, Director M. ELIZABETH CLARKE, Associate Director EDWARD R. URBAN, JR., Program Officer DAN WALKER, Program Officer ROBIN MORRIS, Administrative Associate GLENN MERRILL, Research Associate LORA TAYLOR, Senior Project Assistant JENNIFER SWERDA, Project Assistant SHARI MAGUIRE, Project Assistant ANN CARLISLE, Project Assistant

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--> Commission on Geosciences, Environment, and Resources GEORGE M. HORNBERGER (Chairman), University of Virginia, Charlottesville PATRICK R. ATKINS, Aluminum Company of America, Pittsburgh, Pennsylvania JAMES P. BRUCE, Canadian Climate Program Board, Ottawa, Ontario WILLIAM L. FISHER, University of Texas, Austin JERRY F. FRANKLIN, University of Washington, Seattle THOMAS E. GRAEDEL, Yale University, New Haven, Connecticut DEBRA KNOPMAN, Progressive Foundation, Washington, D.C. KAI N. LEE, Williams College, Williamstown, Massachusetts PERRY L. MCCARTY, Stanford University, California JUDITH E. MCDOWELL, Woods Hole Oceanographic Institution, Massachusetts RICHARD A. MESERVE, Covington & Burling, Washington, D.C. S. GEORGE PHILANDER, Princeton University, New Jersey RAYMOND A. PRICE, Queen's University at Kingston, Ontario THOMAS C. SCHELLING, University of Maryland, College Park ELLEN SILBERGELD, University of Maryland Medical School, Baltimore VICTORIA J. TSCHINKEL, Landers and Parsons, Tallahassee, Florida E-AN ZEN, University of Maryland, College Park Staff MYRON UMAN, Acting Executive Director GREGORY SYMMES, Assistant Executive Director JEANETTE SPOON, Administrative Officer SANDI FITZPATRICK, Administrative Associate MARQUITA SMITH, Administrative Assistant/Technology Analyst

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--> Preface Global marine fish harvest has plateaued and many important commercial stocks have been depleted. The Ocean Studies Board (OSB), at the request of the National Marine Fisheries Service (NMFS), has provided advice designed to improve management of marine fisheries in the United States (NRC, 1994a). Many of the changes suggested in the 1994 report Improving the Management of U.S. Marine Fisheries were incorporated in the reauthorized Magnuson-Stevens Fishery Conservation and Management Act (MSFCMA) in 1996. NMFS also has asked the OSB for advice on specific issues of Atlantic bluefin tuna population biology; the OSB presented its results in another 1994 report, An Assessment of Atlantic Bluefin Tuna (NRC, 1994b). Following the publication of that report, there was a widespread expression of the need for reviews of several other specific stock assessments. NMFS responded by requesting a broad review of the methods used in the United States for stock assessments. The results of that review are presented in this report. This study would not have been possible without the efforts of NMFS scientists who carried out blind runs of data provided by the study committee and participated in the committee's meetings. The cooperation between academic and agency scientists was commendable and actually led to advances in the state of the art of fish stock assessments. The OSB offers sincere thanks to NMFS analysts for their considerable efforts, including Ray Conser, Jeff Fujioka, Wendy Gabriel, Phil Goodyear, Jim Ianelli, Rick Methot, Jerry Pella, Clay Porch, Joe Powers, Mike Prager, Victor Restrepo, Gerald Scott, and Mike Sigler. Other individuals also contributed to the committee's work and deserve the thanks of the committee and the OSB: Jie Zheng (Alaska Department of Fish and Game), Andre Punt (Commonwealth Scientific and Industrial Research Organization, Australia), and David Fournier (Otter Research Ltd.). The results of this study will serve as an important foundation for the National Research Council review of the U.S. Northeast fisheries stock assessments that was mandated by Congress in 1996 as part of the MSFCMA reauthorization. The recommendations presented herein should also be useful to ongoing international activities related to fish stock assessments, such as those of the International Council for the Exploration of the Sea. Kenneth Brink Chairman, Ocean Studies Board

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--> Contents     Executive Summary   1 1   Introduction   7     Overview of U.S. Fisheries   7     Overview of the Use of Assessments in Management   8     Approach of the Committee   12 2   Data   13     Basics of Sample Survey Design   13     Commercial Surveys   15     Recreational Surveys   18     Fishery-Independent Data   21 3   Assessment Methods   27     Review of Existing Methods   27     Bayesian Approaches   31     Meta Analysis   34     Retrospective Analysis in Stock Assessments   35     Data Weighting   36     Uncertainty in Stock Assessment Methods and Models   36 4   Harvest Strategies   37     Indicators of Performance   38     Biological Reference Points   41     Closed-Loop Management Strategies   45     Recreational Management Strategies   52     Impact of Responsible Fishing on Management Strategies and Closed-Loop Performance   54     Evaluation of Management Procedures and Decision Tables   54

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--> 5   Simulations   59     Simulation Approach   59     Simulation Results   64     Implications of Model Results   96 6   Findings and Recommendations   111     How Should Stock Assessments Be Conducted and by Whom?   111     Data Collection and Assessment Methods   112     Harvest Strategies   114     Rigorous Evaluation System   115     New Approaches   115     Peer Review of Assessments and Assessment Methods   116     Education and Training   117     References   119     Appendixes         A. Letter of Request   131     B. Committee Biographies   133     C. Acronyms and Symbols   135     D. Checklist for Stock Assessments   137     E. Description of Age-Structured Simulation Model   141     F. Letter to Analysts   147     G. Retrospective Values   149     H. Information from Interstate Marine Fisheries Commissions and States   153     I. Model Results in Terms of Exploitable and Total Biomass   161     J. Excerpts from the Food and Agricultural Organization Report Precautionary Approach to Fisheries   173     K. Uncertainty in Stock Assessment Methods and Models   175