MARINE MAMMAL POPULATIONS AND OCEAN NOISE
DETERMINING WHEN NOISE CAUSES BIOLOGICALLY SIGNIFICANT EFFECTS
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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 study was supported by Grant No. N00014-03-1-0886 between the National Academy of Sciences and the National Oceanographic Partnership Program with support from the National Oceanic and Atmospheric Administration, Office of Naval Research, National Science Foundation, and the Minerals Management Service. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.
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COMMITTEE ON CHARACTERIZING BIOLOGICALLY SIGNIFICANT MARINE MAMMAL BEHAVIOR
DOUGLAS WARTZOK (Chair),
Florida International University, Miami
JEANNE ALTMANN,
Princeton University, Princeton, New Jersey
WHITLOW AU,
University of Hawaii, Manoa
KATHERINE RALLS,
Smithsonian Institution, Washington, DC
ANTHONY STARFIELD,
University of Minnesota, St. Paul
PETER L. TYACK,
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
Staff
JOANNE BINTZ, Study Director
JENNIFER MERRILL, Study Director
REBECCA NADEL,
Christine Mirzayan Science and Technology Policy Intern
DENISE GREENE, Senior Program Assistant
SARAH CAPOTE, Senior Program Assistant
TERESIA WILMORE, Program Assistant
NORMAN GROSSBLATT, Senior Editor
OCEAN STUDIES BOARD
NANCY RABALAIS (Chair),
Louisiana Universities Marine Consortium, Chauvin
LEE G. ANDERSON,
University of Delaware, Newark
WHITLOW AU,
University of Hawaii, Manoa
ARTHUR BAGGEROER,
Massachusetts Institute of Technology, Cambridge
RICHARD B. DERISO,
Inter-American Tropical Tuna Commission, La Jolla, California
ROBERT B. DITTON,
Texas A&M University, College Station
EARL DOYLE, Shell Oil (retired),
Sugar Land, Texas
ROBERT DUCE,
Texas A&M University, College Station
PAUL G. GAFFNEY, II,
Monmouth University, Long Branch, New Jersey
WAYNE R. GEYER,
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
STANLEY R. HART,
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
RALPH S. LEWIS,
Connecticut Geological Survey (retired), Hartford
WILLIAM F. MARCUSON III,
US Army Corp of Engineers (retired), Vicksburg, Mississippi
JULIAN MCCREARY JR,
University of Hawaii, Honolulu
JACQUELINE MICHEL,
Research Planning, Inc., Columbia, South Carolina
JOAN OLTMAN-SHAY,
Northwest Research Associates, Inc., Bellevue, Washington
ROBERT T. PAINE,
University of Washington, Seattle
SHIRLEY A. POMPONI,
Harbor Branch Oceanographic Institution, Fort Pierce, Florida
FRED N. SPIESS,
Scripps Institution of Oceanography, La Jolla, California
DANIEL SUMAN,
Rosenstiel School of Marine and Atmospheric Science, University of Miami, Florida
Staff
SUSAN ROBERTS, Director
JENNIFER MERRILL, Senior Program Officer
DAN WALKER, Senior Program Officer
ALAN B. SIELEN, Visiting Scholar
ANDREAS SOHRE, Financial Associate
SHIREL SMITH, Administrative Coordinator
JODI BACHIM, Research Associate
NANCY CAPUTO, Research Associate
SARAH CAPOTE, Senior Program Assistant
Preface
Biologically significant is an easy modifier to insert into many descriptors, from habitat designations to pharmacological reactions. It has the attributes of a perfectly reasonable modifier. After all, who would object to putting a limit on the great panoply of varied habitats or potential responses encountered in nature? However, when one attempts to distinguish between biologically significant and biologically not significant, the first question is, To whom? The initial choice of range—from habitat to pharmacology—implies the breadth with which this modifier has been used. Biologically significant changes at the habitat level imply alterations in the composition of species that use a habitat. Biologically significant changes at the pharmacological level imply organism changes. Intermediate between those levels are the population (or stock in marine mammal management terms) and the species.
The most basic goal of the Marine Mammal Protection Act (MMPA) (16 U.S.C. 1361) is to maintain marine mammals as a “significant functioning element in the ecosystem of which they are a part.” The MMPA translates that ecosystem goal to the population level by aiming to ensure that marine mammal stocks do not fall below or are restored to their optimal sustainable population sizes. Although the main goals of the MMPA are defined at the ecosystem and population levels, its primary focus of regulation is at the level of the individual. When the MMPA was enacted, marine mammal populations were threatened by hunting and by deaths resulting
from becoming entangled in nets or otherwise killed in fisheries. The primary regulatory mechanism in the MMPA was a prohibition of the taking of marine mammals; where “take” means to harass, hunt, capture, or kill or attempt to harass, hunt, capture, or kill any marine mammal. The prohibition of taking has reduced the death and injury of marine mammals enough that today many important threats involve habitat degradation and the cumulative effects of harassment. Although harassment is included as a prohibited taking in the MMPA, this prohibition has proved ill suited for protecting marine mammal habitat and regulating cumulative effects.
One approach for protecting marine mammals might be to monitor their populations and initiate protective measures for populations in decline. However, we cannot estimate trends precisely for most marine mammal populations, and by the time a decline is detected, it may be too late. In addition, we also need methods to determine which human activities or natural phenomena are causing population declines or inhibiting population recovery. Many effects of human activities on individual marine mammals occur on a time scale of seconds to years, effects on populations on a scale of years to generations, and effects on ecosystems on a scale of generations to centuries. This report focuses on changes at the population level, but what can be observed are the much faster changes in the behavior and physiology of individuals. The basic goal of this report is to explore the scientific challenge of using short-term observations at the level of individuals to predict effects on populations. Such a predictive model would serve two functions: identifying when the cumulative sum of human effects poses a risk to a population and identifying the activities that pose the greatest risk.
What little we know about behavioral responses of marine mammals to anthropogenic noise highlights the importance of context, including the demographic status of the animals receiving the sound; the characteristics, location, and movement of the sound source; and the location of the animals. The history of the animals is also important: prior exposure to the sound could have resulted in habituation or sensitization. Context includes population status and ecosystem changes; responses that would be insignificant in a population near its carrying capacity can become significant in populations that are depleted or that are encountering multiple stressors, such as El Niño.
Our glimpses into the lives of marine mammals are so short that it is difficult to determine whether the small part of a behavioral reaction we usually can observe is biologically significant. In contrast with Supreme
Court Justice Potter Stewart’s statement with respect to pornography, “I know it when I see it” (Jacobellis v. Ohio, 378 U.S. 184, 197 [1964]), the problem in determining the biological significance of marine mammal responses is that often we do not know them when we see them. Marine mammals are so hard to observe that we may never see serious problems without studies that are targeted to understand their normal behavior and physiology in the wild. A basic tenet of responsible management and conservation is the need to balance the risks posed by overregulation and those posed by underregulation; the latter carry more weight in conditions of greater uncertainty. The depth of our uncertainty in these issues can make it difficult to calibrate the proper extent of precaution.
A reader who expects this volume to provide a “Eureka” moment of insight into the biological significance of marine mammal responses to noise will be disappointed. That should not come as a surprise. Biological significance has not been well defined in many animal groups that are much more amenable to observation than marine mammals and on which much more data are available. The last few decades have seen a rapid increase in studies of the responses of marine mammals to noise, and there is growing evidence that some sounds play a role in lethal strandings of deep-diving beaked whales, but there is not one case in which data can be integrated into models to demonstrate that noise is causing adverse affects on a marine mammal population. In the case of strandings, the primary data gaps are in our ignorance of the population size and status of beaked whales, and our uncertainty about the number of animals killed or injured. For most other noise effects, the primary source of uncertainty stems from our difficulty in determining the effects of behavioral or physiological changes on an individual animal’s ability to survive, grow, and reproduce.
This report contains a conceptual model designed to serve as a roadmap for developing a predictive model that will relate behavioral responses caused by anthropogenic sound to biologically significant, population-level consequences. It identifies the extent of current knowledge and data gaps in each component of the proposed conceptual model to show where research is most needed. In addition to pointing toward a decade-long research agenda for the predictive model, the report suggests management alternatives for the short term and the intermediate term. It also recommends changes in the regulatory structure to include effects of sound on marine mammals within the broader management structure now used exclusively for fisheries. The goal is a common metric for the impact of all human activities on marine mammals and consistent regulation of that impact.
Although a model for predicting the biological significance of different effects cannot be created today, this report offers an approach that can be implemented now to identify, within specified limits, when the responses of marine mammals to anthropogenic noise do not rise to the level of biological significance. The first step in dealing with an apparently intractable problem is to bound it, and this report describes a method for doing that.
Acknowledgments
This report was greatly enhanced by the participants in the workshop held as part of the study. The committee would first like to acknowledge the efforts of those who gave presentations at meetings and thereby helped to set the stage for fruitful discussions in the closed sessions that followed:
JAY BARLOW, Scripps Institution of Oceanography
MELBOURNE BRISCOE, Office of Naval Research
JEAN COCHRANE, US Fish and Wildlife Service
DANIEL P. COSTA, University of California, Santa Cruz
ROGER GENTRY, National Oceanic and Atmospheric Administration National Marine Fisheries Service
WAYNE GETZ, University of California, Berkeley
ROBERT GISINER, Office of Naval Research
DANIEL GOODMAN, Montana State University
BRUCE KENDALL, University of California, Santa Barbara
JAMES KENDALL, Minerals Management Service
S.A.L.M. KOOIJMAN, Vrije Universiteit, Amsterdam
BOB KULL, Parsons
BILL MORRIS, Duke University
TIM RAGEN, Marine Mammal Commission
L. MICHAEL ROMERO, Tufts University
GORDON SWARTZMAN, Applied Physics Laboratory
SHRIPAD TULJAPURKAR, Stanford University
JAMES YODER, National Science Foundation
This report has been reviewed in draft form by persons chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council’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 of 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 for their participation in their review of this report:
HAL CASWELL, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
DAN COSTA, University of California, Santa Cruz
COLLEEN REICHMUTH KASTAK, University of California, Santa Cruz
ROBERT KNOX, University of California, San Diego
ROBERT KULL, Parsons, Norfolk, Virginia
PAUL NACHTIGALL, University of Hawaii, Kailua
DON SINIFF, University of Minnesota, St. Paul
NINA YOUNG, The Ocean Conservancy, Washington, DC
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 John Dowling, Harvard University, and Andrew Solow, Woods Hole Oceanographic Institution, appointed by the National Research Council, who were responsible for making certain that an independent examination of the report was carried out in accordance with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of the report rests entirely with the committee and the institution.