Effects of Trawling and Dredging on Seafloor Habitat

Committee on Ecosystem Effects of Fishing: Phase 1—Effects of Bottom Trawling on Seafloor Habitats

Ocean Studies Board

Division on Earth and Life Studies

National Research Council

NATIONAL ACADEMY PRESS
Washington, D.C.



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Effects of Trawling and Dredging on Seafloor Habitat Effects of Trawling and Dredging on Seafloor Habitat Committee on Ecosystem Effects of Fishing: Phase 1—Effects of Bottom Trawling on Seafloor Habitats Ocean Studies Board Division on Earth and Life Studies National Research Council NATIONAL ACADEMY PRESS Washington, D.C.

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Effects of Trawling and Dredging on Seafloor Habitat NATIONAL ACADEMY PRESS 2101 Constitution Ave., N.W. Washington, DC 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 competences and with regard for appropriate balance. This report and the committee were supported by a grant from the National Marine Fisheries Service. The views expressed herein are those of the authors and do not necessarily reflect the views of the sponsors. This paper is funded in part by a contract from the National Oceanic and Atmospheric Administration. The views expressed herein are those of the author(s) and do not necessarily reflect the views of NOAA or any of its subagencies. Library of Congress Control Number: 2002105183 International Standard Book Number: 0-309-08340-0 Additional copies of this report are available from: National Academy Press 2101 Constitution Avenue, N.W. Box 285 Washington, DC 20055 800-624-6242 202-334-3313 (in the Washington Metropolitan area) http://www.nap.edu Copyright 2002 by the National Academy of Sciences. All rights reserved. Printed in the United States of America.

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Effects of Trawling and Dredging on Seafloor Habitat THE NATIONAL ACADEMIES National Academy of Sciences National Academy of Engineering Institute of Medicine National Research Council 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 for 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. Wm. 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 Alberts and Dr.Wm. A. Wulf are chairman and vice-chairman, respectively, of the National Research Council.

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Effects of Trawling and Dredging on Seafloor Habitat COMMITTEE ON ECOSYSTEM EFFECTS OF FISHING: PHASE 1—EFFECTS OF BOTTOM TRAWLING ON SEAFLOOR HABITATS JOHN STEELE, Chair, Woods Hole Oceanographic Institution, Massachusetts DAYTON LEE ALVERSON, Natural Resource Consultants, Seattle, Washington PETER AUSTER, University of Connecticut, Groton JEREMY COLLIE, University of Rhode Island, Narragansett JOSEPH T. DEALTERIS, University of Rhode Island, Kingston LINDA DEEGAN, Marine Biological Laboratory, Woods Hole, Massachusetts ELVA ESCOBAR-BRIONES, Universidad Nacional Autonoma de Mexico, Cuidad Universitaria STEPHEN J. HALL, Australian Institute of Marine Science, Townsville, Queensland GORDON H. KRUSE, University of Alaska, Fairbanks CAROLINE POMEROY, University of California, Santa Cruz KATHRYN M. SCANLON, U.S. Geological Survey, Woods Hole, Massachusetts PRISCILLA WEEKS, University of Houston, Clear Lake, Texas Staff SUSAN ROBERTS, Study Director JODI BACHIM, Senior Project Assistant ABBY SCHNEIDER, NRC Fellow

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Effects of Trawling and Dredging on Seafloor Habitat OCEAN STUDIES BOARD NANCY RABALAIS, Chair, Louisiana Universities Marine Consortium, Chauvin ARTHUR BAGGEROER, Massachusetts Institute of Technology, Cambridge JAMES COLEMAN, Louisiana State University, Baton Rouge LARRY B. CROWDER, Duke University Marine Laboratory, Beaufort, North Carolina G. BRENT DALRYMPLE, Oregon State University (ret.), Corvallis RICHARD B. DERISO, Inter-American Tropical Tuna Commission, La Jolla, California EARL DOYLE, Shell Oil (ret.), Sugar Land, Texas ROBERT DUCE, Texas A&M University, College Station WAYNE R. GEYER, Woods Hole Oceanographic Institution, Massachusetts D. JAY GRIMES, University of Southern Mississippi, Ocean Springs MIRIAM KASTNER, Scripps Institution of Oceanography, La Jolla, California CINDY LEE, State University of New York, Stony Brook RALPH S. LEWIS, Connecticut Geological and Natural History Survey, Hartford BONNIE MCCAY, Rutgers University, New Brunswick, New Jersey JULIAN P. MCCREARY, JR., University of Hawaii, Honolulu JACQUELINE MICHEL, Research Planning, Inc., Columbia, South Carolina RAM MOHAN, Blasland, Bouck & Lee, Inc., Annapolis, Maryland SCOTT NIXON, University of Rhode Island, Narragansett JON G. SUTINEN, University of Rhode Island, Kingston NANCY TARGETT, University of Delaware, Lewes PAUL TOBIN, Xtria, LLC, Chantilly, Virginia Staff MORGAN GOPNIK, Director SUSAN ROBERTS, Senior Program Officer DAN WALKER, Senior Program Officer JOANNE BINTZ, Program Officer JENNIFER MERRILL, Program Officer TERRY SCHAEFER, Program Officer JOHN DANDELSKI, Research Associate ROBIN MORRIS, Financial Officer SHIREL SMITH, Administrative Associate JODI BACHIM, Senior Project Assistant NANCY CAPUTO, Senior Project Assistant DENISE GREENE, Senior Project Assistant DARLA KOENIG, Senior Project Assistant JULIE PULLEY, Project Assistant ALISON SCHRUM, Project Assistant

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Effects of Trawling and Dredging on Seafloor Habitat Preface The Ocean Studies Board has provided advice to Congress and the National Marine Fisheries Service on a broad range of topics relevant to marine fisheries. Sustaining Marine Fisheries dealt broadly with the ecological issues (National Research Council, 1999) while other reports have focused on the science of fisheries management: Review of Northeast Fishery Stock Assessments (National Research Council, 1998), Improving Fish Stock Assessments (National Research Council, 1999), and Improving the Collection, Management and Use of Marine Fisheries Data (National Research Council, 2001). Several reports have reviewed management methods including Marine Protected Areas: Tools for Sustaining Ocean Ecosystems (National Research Council, 2001) and Sharing the Fish: Toward a National Policy on Individual Fishing Quotas (National Research Council, 2000). An emergent theme in nearly all these reports is the desire to reconcile conflicting demands for protecting marine environments, sustaining fishery yields, and responding to the social and economic interests of the fishery and fishing communities. Such reconciliation must integrate scientific and technical information with the diversity of human priorities. This plurality was a central feature of our workshop meetings in Boston, Galveston, and Anchorage with representatives of the fishing industry, environmental groups and members of state and federal agencies. Our report has benefited significantly from the presentations and discussions at these meetings. The committee would first like to acknowledge the efforts of those who gave presentations: Frank Almeida, Bill Amaru, Pam Baker, Mike Barnette, Francine Bennis, Eloise Brown, Ralph Brown, Arnie Carr, Anthony Chatwin, Jim Churchill, Felicia Coleman, Cathy Coon, Chris Dorsett, Ben Enticknap, Benny Gallaway, John Gauvin, Caroline Gibson, David Goethel, Don Gordon, Alonzo Hamilton, David Harrington, Bill Hayes, Jon Heifetz, Tom Hill, Teressa Kandianis, Rick Leard, Gary Loverich, Trevor McCabe, Linda Mercer, Chris Oliver, Mike Payne, Mark Powell, Jeff Rester, Andy Rosenberg, Brian Rothschild, Pete Sheridan, Michael Sissenwine, Nils Stolpe, Les Watling, Dave Witherell, and Chris Zeman. These talks helped set the stage for fruitful discussions in the closed sessions that followed. This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their participation in their review of this report: ARNE CARR, Massachusetts Department of Fisheries, Pocasset FELICIA COLEMAN, Florida State University, Tallahassee CAROLINE GIBSON, Pacific Marine Conservation Council, Friday Harbor, Washington

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Effects of Trawling and Dredging on Seafloor Habitat DANIEL HUPPERT, University of Washington, Seattle BRIAN ROTHSCHILD, University of Massachusetts, Dartmouth MICHAEL SINCLAIR, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations nor did they see the final draft of the report before its release. The review of this report was overseen by NANCY MARCUS, Florida State University, Tallahassee, appointed by the Divison on Earth and Life Studies, who was responsible for making certain that an independent examination of this report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring committee and the institution. The committee is also grateful to Andrea Dunn for compiling information about the regional fisheries that comprises Table 4.2. Jim Lester also provided important material for this report. The committee wishes to thank the staff at the Ocean Studies Board for their efforts in support of this study: Jodi Bachim, Senior Project Assistant and Abby Schneider, National Research Council Fellow. The committee is especially grateful to the Study Director Dr. Susan Roberts who not only had the task of integrating the individual contributions from committee members into a coherent report, but also guided the report through the extensive process of review and revision. John Steele Chair

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Effects of Trawling and Dredging on Seafloor Habitat Contents     Executive Summary   1 1   Introduction   7     Study Approach and Report Organization,   8     Legislative Context,   8     Identifying Essential Fish Habitat,   11 2   Characterization of Fishing Gear   12     Dredge Gear,   13     Trawl Gear,   14     Beam Trawls,   14     Otter Trawls,   14     Conclusion,   16 3   Effects of Trawling and Dredging   18     Direct Effects on Species and Habitat Structure,   19     Research Approaches,   19     Research Summary,   20     Modeling Mortality in Relation to Fishing Effort,   23     Modifications to Habitat Structure,   24     Indirect Effects,   26     Sediment Processes,   26     Species Interactions,   26     Rates of Recovery,   27     Uncertainty,   28     Summary,   29     Research Needs,   29 4   Habitat Mapping and Distribution of Fishing Effort   30     Habitat,   30     Habitat Classification,   30     Bathymetry,   32     Geologic Structure and Substrate,   32

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Effects of Trawling and Dredging on Seafloor Habitat     Geographic Information System,   36     Questions of Scale,   36     Distribution and Intensity of Fishing Effort,   37     Regional Fisheries,   39     New England: Maine to Connecticut,   39     Mid-Atlantic: New York to Virginia,   42     South Atlantic: North Carolina to Eastern Florida,   43     Gulf of Mexico: Western Florida to Texas,   44     Pacific: California, Oregon, and Washington,   44     North Pacific: Alaska,   46     Conclusion,   47 5   Analyzing the Risk to Seafloor Habitats   48     Framework for Decisionmaking,   48     Exposure Assessment Model,   49     Research,   50     Risk Assessment,   50     Risk Management,   51     Comparative Risk Assessment,   52     Description of Criteria,   53     Summary,   54 6   Management Options   57     Gear Modifications,   57     Closed Areas,   59     Effort Reduction,   61     Conclusion,   63 7   Findings and Recommendations   65     Recommendations,   66     Interpretation and Use of Existing Data,   66     Integration of Management Options,   66     Policy Issues Raised by Existing Legislation,   67     Future Research,   67     Gear Impacts and Modification,   67     Habitat Evaluation,   68     Management,   68     References   69     Appendixes         A Committee and Staff Biographies   77     B Regional Distribution of Fishing Effort   80     C Mapping Tools   120     D Workshop Agendas   122     E Acronyms   126