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DECLINE OF THE
SEA TURTLES
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DECLINE 0' THE
SEA TURTLES
CAUSES AND PREVENTION
Committee on Sea Turtle Conservation
Board on Environmental Studies anc! Toxicology
Boarcl on Biology
Commission on Life Sciences
National Research Council
NATIONAL ACADEMY PRESS
Washington, D.C. 1990
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NATIONAL ACADEMY PRESS 2101 Constitution Avenue, N.W. Washington, D.C.
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 has been reviewed by a group other than the authors according to proce-
dures 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 project was supported by the Department of Commerce under contract number 50
DGNC 9 00080.
Cover: Loggerhead turtle. Photograph courtesy of the Florida Audubon Society.
Frontispiece: Thousands of fish and a loggerhead turtle caught in a shrimp trawl. The turtle
is alive and apparently uninjured. The fish are dead. Photograph: Michael Weber, Center
for Marine Conservation.
Photographs on chapter-opening pages are courtesy of Peter Pritchard and the Florida
Audubon Society, and Michael Weber, Center for Marine Conservation.
Library of Congress Cataloging-in-Publication Data
Decline of the sea turtles: causes and prevention /
Committee on Sea Turtle Conservation, Board on Environ-
mental Studies and Toxicology, Board on Biology, Com-
mission on Life Sciences, National Research Council.
p. cm.
Includes bibliographical references and index.
ISBN 0-309-04247-X: $14.95
1. Sea turtles. 2. Endangered species. 3. Wildlife conservation
I. National Research Council (U.S.). Committee on Sea Turtle Conservation.
QL666.C536D43 1990
639.9'7792--dc20
Copyright ~1990 by the National Academy of Sciences
90-38318
CIP
No part of this book may be reproduced by any mechanical, photographic, or electronic
process, or in the form of a phonographic recording, nor may it be stored in a retrieval sys-
tem, transmitted, or otherwise copied for public or private use, without written permission
from the publisher, except for the purposes of official use by the U.S. government.
Printed in the United States of America
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Decline of the Sea Turtles
CommiNee on Sea Turde Conservation
,lohn,,. Magnuson, Chair, University of Wisconsin, Madison
Karen A. Bjorndal, University of Florida, Gainesville
William D. DuPaul, Virginia Institute of Marine Science,
College of William and Mary, Gloucester Point
Gary L. Graham, Texas A&M University, College Station
David W. Ovens, Texas A&M University, College Station
Charles H. Peterson, University of North Carolina, Morehead City
Peter C. H. Pritchard, Florida Audubon Society, Maitland
James I. Richardson, University of Georgia, Athens
Gary E. Saul, FTN Associates, Austin, Texas
Charles W. West, Nor'Eastern Trawl Systems, Bainbridge Island,
Washington
Project Staff
David,,. Policansky, Program Director
Dave,iohnston, Project Director
Norman Grossblatt, Editor
Bernidean Williams, Information Specialist
Linda B. Kegley, Project Assistant
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iv
Decline of the Sea Turtles
Board on Environmental ShJdies and Toxicology
Gilbert S. Omenn, Chair, University of Washington, Seattle
Frederick R. Anderson, Washington School of Law, American
University, Washington, D.C.
John Bailar, McGill University School of Medicine, Montreal, Quebec
Lawrence W. Barnthouse, Oak Ridge National Laboratory, Oak Ridge,
Tennessee
David Bates, University of British Columbia, Vancouver
Joanna Burger, Rutgers University, Piscataway, New Jersey
Yoram Cohen, University of California, Los Angeles
John L. Emmerson, Eli Lilly & Company, Greenfield, Indiana
Robert L. Harness, Monsanto Agricultural Company, St. Louis, Missouri
Paul,}. Lloy, UMDNI-Robert Wood Johnson Medical School, Piscataway,
New Jersey
bane Lubehenco, Oregon State University, Corvallis
Donald Mattison, University of Arkansas for Medical Sciences,
Little Rock
Duncan T. Patten, Arizona State University, Tempe
Nathaniel Reed, Hobe Sound, Florida
William H. Rodgers, University of Washington, Seattle
F. Sherwood Rowland, University of California, Irvine
Liane B. Russell, Oak Ridge National Laboratory, Oak Ridge, Tennessee
Milton Russell, University of Tennessee, Knoxville
John H. Seinfeld, California Institute of Technology, Pasadena
I. Glenn Sipes, University of Arizona, Tucson
Bruce M. Alberts bex officioJ, University of California, San Francisco
Donald Hornig Sex officio", Harvard School of Public Health, Boston,
Massachusetts
Paul Risser (ex officio", University of New Mexico, Albuquerque
Staff
,iames,,. Reisa, Director
David,}. Policansky, Applied Ecology and Natural Resources Program
Director
Robert Smudge, Exposure Assessment and Risk Reduction Program
Director
Richard D. Thomas, Human Toxicology and Risk Assessment Program
Director
Lee R. Paulson, Manager, Toxicology Information Center
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Decline of the Sea Turtles
Board on Biology
Francisco,'. Ayala, Chair, University of California, Irvine
Nina V. Fedoroff, Carnegie Institution of Washington, Baltimore
Maryland
Timothy H. Goldsmith, Yale University, New Haven, Connecticut
Ralph W. F. Hardy, Boyce Thompson Institute for Plant Research,
Ithaca, New York
Ernest G.,laworski, Monsanto Company, St. Louis, Missouri
Harold A. Mooney, Stanford University, Stanford, California
Harold,,. Morowitz, George Mason University, Fairfax, Virginia
Mary Lou Pardue, Massachusetts Institute of Technology, Cambridge
David D. Sabatini, New York University, New York
Michael E. Soule, University of Michigan, Ann Arbor
Malcolm S. Steinberg, Princeton University, Princeton, New Jersey
David B. Wake, University of California, Berkeley
Bruce M. Alberts (ex officio", University of California, San Francisco
Oskar R. Zaborsky, Director
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Decline of the Sea Turtles
Commission on Life Sciences
Bruce M. Alberts, Chair, University of California, San Francisco
Bruce N. Ames, University of California, Berkeley
Francisco,}. Ayala, University of California, Irvine
,'. Michael Bishop, University of California Medical Center, San Francisco
Freeman,'. Dyson, Institute for Advanced Study, Princeton, New lersey
Nina V. Fedoroff, Carnegie Institution of Washington, Baltimore,
Maryland
Ralph W. F. Hardy, Boyce Thompson Institute for Plant Research
(Cornell University), Ithaca, New York
Leroy E. Hood, California Institute of Technology, Pasadena
Donald F. Hornig, Harvard School of Public Health, Boston,
Massachusetts
Ernest G.,iaworski, Monsanto Company, St. Louis, Missouri
Marian E. Koshland, University of California, Berkeley
Harold A. Mooney, Stanford University, Stanford, California
Steven P. Pakes, University of Texas, Dallas
Joseph E. Rall, National Institutes of Health, Bethesda, Maryland
Richard D. Remington, University of Iowa, Iowa City
Paul G. Risser, University of New Mexico, Albuquerque
Richard B. Sallow, Brookhaven National Laboratory, Upton, New York,
New York
Torsten N. Wiesel, Rockefeller University, New York, New York
John E. Burris, Executive Director
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Preface
The Committee on Sea Turtle Conservation was formed on March 1,
1989, under the auspices of the Board on Environmental Studies and Tox-
icology (BEST) and the Board on Biology of the National Research Coun-
cil's Commission on Life Sciences. The committee was formally charged
as follows:
The task of this committee is to perform a study mandated by
the Endangered Species Act Amendments of 1988, reviewing
scientific and technical information pertaining to the conserva-
tion of sea turtles and the causes and significance of turtle
mortality, including that caused by commercial trawling. The
committee's report will provide information on the population
biology, ecology, and behavior of five endangered or threat-
ened species: the Kemp's ridley, loggerhead, leatherback,
hawksbill, and green sea turtles. The committee will also
review information on the effectiveness of current and needed
programs to increase turtle populations. The resulting report
will be used by the Secretary of Commerce to assess the effec-
tiveness of and need for regulations requiring the use of turtle-
excluder devices (TEDs) by commercial shrimp-trawlers.
. .
v''
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vial
Decline of the Sea Turtles
In addition to this final report, the committee was required to prepare
an interim report on the status of the Kemp's ridley (see Section 1008 of
the Endangered Species Act Amendments of 1988 in Appendix A). The
interim report on Kemp's ridley is enclosed as Appendix B.
The committee met on May 4-5, June 26-29, September 28-30, and
November 16-18, 1989. In addition, a writing group met in Washington,
D.C., on December 4-5, 1989.
The committee was fortunate to have as members experts on turtle
biology, physiology, and conservation, shrimp fishing and gear technolo-
gy (in particular, trawl and TED technology), fishery biology and manage-
ment, and technology transfer and fishery extension programs. All these
kinds of expertise were required to address the complex issues of sea tur-
tle conservation. I was especially pleased by the new analyses and syn-
theses that the committee was able to make that allowed us to reach a
number of important conclusions with more certainty than I originally had
expected.
To gain further knowledge of TEDs and other gear operations, the
committee sailed for a day off the coast of Jekyll Island, Georgia, on the
RV/Georgia Bulldog. The trip was made possible through the courtesy of
David Harrington.
We were assisted greatly by the National Research Council staff, in par-
ticular, Dave Johnston, our project director, and Linda Kegley, our project
assistant. We also acknowledge the guidance of David Policansky, pro-
gram director; James ]. Reisa, director of BEST; and Joanna Burger, our
BEST liaison. In addition to those persons, other BEST staff jumped in to
help when needed. Bernidean Williams, information specialist, helped to
check references. Norman Grossblatt of the Commission on Life Sciences
and Lee ' Paulson of BEST edited the report. My personal thanks to them
all.
We also thank a number of persons who either prepared presentations
for the committee or made original data available to the committee for
analysis and interpretation. 'Those who provided testimony were Michael
Weber (Center for Marine Conservation), Larry Ogren (National Marine
Fisheries Service), Earl Possardt (U.S. Fish and Wildlife Service), Charles
Oravetz (National Marine Fisheries Service), Tee John Mialjevich (Con-
cerned Shrimpers of America), Carol Ruckdeschel (Cumberland Museum),
David Harrington (University of Georgia Marine Extension Service), Joe
Webster (Commercial Shrimp Fisherman), David Blouin (Department of
Experimental Statistics, Louisiana State University), Elizabeth Gardner (leg-
islative assistant to Senator Howell Heflin), and David Cottingham
(National Marine Fisheries Service). Those who provided data include
Wendy Teas, Nancy Thompson, Terry Henwood, Warren Stuntz, Edward
F. Klima, Ren Lohoefener, Ernie Snell, James Nance, and Guy Davenport,
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Decline of the Sea Turtles
all with the National Marine Fisheries Service; Alan Bolten (University of
Florida); Michael Harris (Georgia Department of Natural Resources); Tom
Henson (North Carolina Nongame Endangered Wildlife Program); and
Sally Murphy (South Carolina Wildlife and Marine Resources). Without
their assistance we would not have been able to make our report current.
I wish to thank my own colleagues in the Center for Limnology at the
University of Wisconsin-Madison, who assisted with analyses and data
transfer: Chris Carr, Barbara I. Benson, Inga Larson, Norma D. Magnuson,
Mark D. McKenzie, Mary Rose Lawocki Smith, and Joyce M. Tynan. Assis-
tance to other committee members was provided by Nancy Balcom (Vir-
ginia Institute of Marine Science), David Rostal (Texas A&M University),
and Hal Summerson and Alberto Reyes-Campo (University of North Car-
olina, Institute of Marine Sciences).
We dedicate this volume to the peaceful coexistence of sea turtles and
shrimp fisheries.
John J. Magnuson
Chairman
April 23, 1990
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The National Academy of Sciences is a private, nonprofit, self-perpetu-
ating society of distinguished scholars engaged in scientific and engineer-
ing 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. Frank Press is president of the National Academy of Sci
ences.
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 Sci-
ences the responsibility for advising the federal government. The Nation-
al Academy of Engineering also sponsors engineering programs aimed at
meeting national needs, encourages education and research, and recog-
nizes the superior achievements of engineers. Dr. Robert M. White 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. Samuel O. Thier is
president of the Institute of Medicine.
The National Research Council was organized by the National Acade-
my 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 princi-
pal operating agency of both the National Academy of Sciences and the
National Academy of Engineering in providing services to the govern-
ment, the public, and the scientific and engineering communities. The
Council is administered jointly by both Academies and the Institute of
Medicine. Dr. Frank Press and Dr. Robert M. White are chairman and
vice chairman, respectively, of the National Research Council.
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Contents
EXECUTIVE SUMMARY
1 INTRODUCTION
2 BIOLOGY.................
Kemp's Ridley, 23
Loggerhead, 28
Green Turtle, 32
Hawksbill, 35
Leatherback, 39
Olive Ridley, 41
3 POPULATION TRENDS
Kemp's Ridley, 43
Loggerhead, 47
Green Turtle, 48
Hawksbill, 48
Leatherback, 49
Summary, 49
.16
X!
.42
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4 DISTRIBUTION OF SEA TURTLES IN U.S. WATERS 51
Sources of Information, 51
Distribution, 54
Onshore, Offshore, and Depth Distribution, 58
Summary, 60
5 NATURAL MORTALITY AND CRITICAL LIFE STAGES .
Biotic Sources of Mortality, 62
Abiotic Sources of Mortality, 66
Quantitative Studies of Natural Mortality, 67
Summary, 72
....... 61
6 SEA TURTLE MORTALLY ASSOCIATED WITH
HUMAN AClIVlT~S 74
Mortality of Sea Turtle Eggs and Hatchlings, 77
Mortality of Sea Turtle Juveniles and Adults, 82
Summary, 116
7 CONSERVATION MEASURES
Rationale and Objective of the Recovery Plan, 119
Description of Conservation Measures, 120
Reducing Adult and Subadult Mortality
Associated with Human Activities, 125
Education and Technology Transfer, 140
Conservation Efforts in Other Jurisdictions, 142
8 CONCLUSIONS AND RECOMMENDATIONS
Conclusions, 144
Recommendations, 146
REFERENCES
APPENDIXES
.118
144
154
A. ENDANGERED SPECIES ACT
AMENDMENTS OF 1988 175
B. INTERIM REPORT, COMMIT1't;E ON
SEA TURTLE CONSERVATION 179
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Decline of the Sea Turtles
C. ILLUSTRATIONS OF TURTLE
EXCLUDER DEVICES 193
D. AERIAL SURVEY DATA OF SEA TURTLES
IN FISHING ZONES..................................................................
.199
E. SEA TURTLE STRANDING DATA 202
F. SHRIMP FISHING EFFORT
G. ANNOTATED AND CHRONOLOGICAL
LIST OF EDUCATIONAL EFFORTS
ON TEDs FOR FISHERMEN BY
NATIONAL MARINE FISHERIES SERVICE 218
.215
H. ANNOTATED AND CHRONOLOGICAL
LIST OF EDUCATIONAL EFFORTS ON
TEDs FOR FISHERMEN BY SEA GRANT 224
I. NEWSLE'l~l'~RS AND NOTICES PERTAINING
TO TEDs 238
J. BIOGRAPHIES OF
COMMI'l~l'~E MEMBERS...........................................................
.249
INDEX 253