ISBN-10:
0520248848
ISBN-13:
9780520248847
Pub. Date:
01/16/2007
Publisher:
University of California Press
Whales, Whaling, and Ocean Ecosystems / Edition 1

Whales, Whaling, and Ocean Ecosystems / Edition 1

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Product Details

ISBN-13: 9780520248847
Publisher: University of California Press
Publication date: 01/16/2007
Edition description: First Edition
Pages: 418
Product dimensions: 8.50(w) x 11.00(h) x 1.20(d)

About the Author


James A. Estes is Research Biologist with the U.S. Geological Survey and Adjunct Professor of Biology at the University of California, Santa Cruz. He is coeditor of Community Ecology of Sea Otters. Douglas P. DeMaster is Director of the Alaska Fisheries Science Center. Daniel F. Doak and Terrie M. Williams are Professors of Biology at the University of California, Santa Cruz. Doak is coauthor of Quantitative Conservation Biology and Williams is author of The Hunter's Breath: On Expedition with the Weddell Seals of the Antarctic. Robert L. Brownell is Senior Scientist with the Southwest Fisheries Science Center.

Read an Excerpt

Whales, Whaling, and Ocean Ecosystems


By J.A. Estes

University of California Press

Copyright © 2006 Regents of the University of California
All right reserved.




Chapter One

Introduction

JAMES A. ESTES

Overharvesting has led to severe reductions in the abundance and range of nearly every large vertebrate species that humans have ever found worth pursuing. These megafaunal reductions, dating in some cases from first contact with early peoples (Martin 1973), are widely known. In contrast, remarkably little is known about the ecological consequences of megafaunal extirpations. Whales and whaling are part of that legacy. Most people know that large whales have been depleted, but little thought has been given to how the depletions may have influenced ocean ecosystems. This volume is an exploration of those influences.

My own interest in the ecological effects of whaling has a complex and serendipitous history, beginning with a view of species interactions strongly colored by first-hand observations of the dramatic and far-reaching influence of sea otters on kelp forest ecosystems (Estes and Palmisano 1974; Duggins et al. 1989; Estes et al. 2004). Sea otters prey on herbivorous sea urchins, thus "protecting" the kelp forest from destructive overgrazing by unregulated sea urchin populations. The differences between shallow reef systems with and without sea otters are every bit as dramatic and far-reaching as those that exist between clear-cuts and old growth forests on the land. I had longthought that the sea otter-kelp forest story was an unusual or even unique case, but have now come to realize that many other species of large vertebrates exert similarly important ecological influences on their associated ecosystems and that today's world is a vastly different place because of what we have done to them. Accounts of the influences of elephants in Africa (Owen-Smith 1988); wolves in North America (McLaren and Peterson 1994; Ripple and Larsen 2000; Berger et al. 2001); coyotes in southern California (Crooks and Soulé 1999); fishes in North American lakes (Carpenter and Kitchell 1993) and rivers (Power 1985); large carnivores in Venezuela (Terborgh et al. 2001); and what Janzen and Martin (1982) termed "neotropical anachronisms"-dysfunctional ecosystems resulting from early Holocene extinctions of the New World megafauna-provide compelling evidence for significant food web effects by numerous large vertebrates in a diversity of ecosystems. This view was recently reinforced by the realization that coastal marine ecosystems worldwide have collapsed following historical overfishing (Jackson et al. 2001). The belief that whaling left an important imprint on ocean ecosystems was easy to embrace.

That belief, however, was founded far more on principle and analogy than it was on empirical evidence. My real entrée into the ecology of whales and whaling was set off by a seemingly unrelated event-the collapse of sea otters in southwest Alaska. In truth, the possibility that the sea otter's welfare was in any way related to whaling never dawned on me until recently. But the search for an explanation of the sea otter decline led my colleagues and me to increased predation by killer whales as the likely cause (Estes et al. 1998), although at the time we didn't understand why this happened. However, we knew that various pinnipeds in the North Pacific Ocean and southern Bering Sea had also declined in the years preceding the sea otter collapse and thus surmised that a dietary switch by some of the pinniped-eating killer whales may have caused them to eat more sea otters. In the search for an ultimate cause, we therefore presumed that factors responsible for the pinniped declines were also responsible for the sea otter collapse. Like most others at that time, we believed that the pinniped declines had been driven by nutritional limitation, the purported consequence of ocean regime shifts and/or competition with fisheries (Alaska Sea Grant 1993; National Research Council 1996). However, that belief changed from acceptance to suspicion to doubt as a number of inconsistencies and uncertainties with the nutritional limitation hypothesis became apparent (National Research Council 2003). This growing doubt, coupled with evidence that killer whales had caused the sea otter decline, made it easy to imagine that predation by killer whales was responsible for the pinniped declines as well. Demographic and energetic analyses of killer whales and their prey indicated that this possibility was imminently feasible, and in the admittedly complex ecological milieu of the North Pacific Ocean and southern Bering Sea it seemed the most parsimonious explanation. As we assembled additional information, two remarkable patterns emerged-first, that the coastal marine mammal declines began in earnest following the collapse of the last phase of industrial whaling in the North Pacific Ocean; second, that the various populations of pinnipeds and sea otters declined sequentially, one following the next in a seemingly well-ordered manner. These patterns led us to surmise that whaling was likely an important driver of the megafaunal collapse, the proposed mechanism being a dietary shift by killer whales from great whales to other, smaller marine mammal species after the great whales had become sufficiently rare (Springer et al. 2003). This hypothesis, though admittedly simplistic and immensely controversial, stimulated my interest in the connection between whales and ocean food webs.

The question of how whales and whaling influenced ocean food webs is a much broader one, both from the standpoints of process and geography. The idea of a book to consider these larger issues arose from discussions with Dan Doak and Terrie Williams. We recognized that any such effort would require people with expertise on the great whales. Bob Brownell and Doug DeMaster thus joined us. A little further thought led us to identify three main pathways by which the great whales, and their demise due to whaling, may have influenced ocean food webs. One such pathway was as prey for other predators, along the lines of the hypothesis summarized in the preceding paragraphs-a sort of bottom-up effect with indirect food web consequences. Another pathway for the great whales was as consumers-a top-down effect in the traditional sense. The third potentially important food web pathway for the great whales was as detritus-effects on the flux of carbon and other nutrients via scavengers and other detritivores. These food web pathways provide a roadmap for where and how to look for the influences of whales and whaling on ocean ecosystems. The big question, of course, is whether or not any or all of these imagined pathways are important. At one extreme, the great whales may be little more than passengers in ocean ecosystems largely under the control of other processes. At the other extreme is the possibility that one or more of these pathways drive the structure and function of ocean ecosystems in significant ways. Given the enormous number of whales that inhabited the world's oceans before the whalers took them, the diversity of habitats they occupied and prey they consumed, and their large body sizes and high metabolic rates, it is easy to imagine that their losses were important ecologically.

Imagining and knowing, however, are very different things. The problem before us is to evaluate the potential effects of whales and whaling on ocean ecosystems in rigorous and compelling ways, and the challenges of this task are substantial. For one, the events of interest are behind us. We have relatively little information on ocean ecosystems from earlier periods when whales were abundant. This difficulty is compounded by the facts that estimates of abundance for many of the whale populations are poorly known and that the ocean environment is highly dynamic. Climate regime shifts have important effects on production, temperature, and the distribution and abundance of species (Mantua and Hare 2002; Chavez et al. 2003). El Niño-Southern Oscillation (ENSO) events, which have been widely recognized and carefully studied only during the past several decades, exert strong influences on ocean ecosystems over even shorter time periods (Diaz and Pulwarty 1994). Furthermore, open ocean ecology seems to have focused almost exclusively on bottom-up forcing processes. Although no reasonable scientist could possibly believe that bottom-up forcing does not influence the dynamics of ocean ecosystems, the focus on this perspective of food web dynamics and population regulation has relegated species at higher trophic levels to an implicit status of passengers (as opposed to drivers) in ocean ecosystem dynamics. Finally, large whales are not the only organisms to have been removed in excess from the world oceans. Immense numbers of predatory fishes also have been exploited, substantially reducing many populations before, during, and after the whaling era (Pauly et al. 1998, 2002). The largely unknown food web effects of these fisheries, while potentially of great importance, confound our efforts to understand the effects of whales and whaling on ocean ecosystems.

The news is not all bad. There are reasons to hope that significant progress will be made in understanding the ecological consequences of whales and whaling. Ocean ecosystems have been perturbed by the removal of large whales. A great experiment was thus done, and if this experiment did create significant change, records of that change surely exist. The trick is finding them. Such records might be discovered in anoxic basin sediment cores, isotopic analyses, or any number of historical databases looked at with the question of whaling in mind. Another useful feature of the problem is that the effects of whaling were replicated at different times and places. This spatio-temporal variation in the demise of whale populations offers further opportunity for analyses. Finally, none of the great whales have been hunted to global extinction. With protection, most populations that have been monitored have started to recover (Best 1993), and some may have fully recovered (e.g., the eastern North Pacific gray whale). Thus there is the potential for recovery of not only the whales but of their food web interactions, and the opportunity to watch this happen in real time. A more powerful instrument of learning is difficult to imagine.

Understanding the effects of whales and whaling on ocean ecosystems is a complex problem. The unraveling of what one might know and learn requires people with diverse interests and experience. We have attempted to assemble an appropriately eclectic group to write this book. Some of the authors are experts on the biology and natural history of the great whales; their knowledge is also essential to the reconstruction of what happened during the era of industrial whaling. Other authors, while perhaps knowing little about whales, were invited because of their expertise in such diverse areas as history, economics, policy, physiology, demography, genetics, paleontology, and interaction web dynamics. Still others were invited because of their knowledge of other ecosystems in which either the perspective of process differs from that of ocean ecologists or the evidence for ecological roles of large vertebrates is clearer.

The volume is divided into five sections. The first (Background) provides a backdrop by reviewing the theory and evidence for food web processes and summarizing what is known about the history and ecological role of large consumers in other ecosystems. The second section (Whales and Whaling) presents a variety of relevant information on the natural history of whales and on the consequences of whaling to the whales themselves, including several accounts focusing specifically on killer whales and killer whale-large whale relationships. The third section (Process and Theory) examines how and why food web interactions involving great whales might occur. Relevant aspects of their morphology and physiology as well as general assessments of their potential roles as predators, prey, and detritus are presented in this section. The fourth section (Case Studies) includes a variety of more specific accounts of the effects of whales and whaling in various ocean ecosystems. This is necessarily the book's most diverse and unstructured section, because we are asking the question retrospectively; the evidence has not been gathered in a systematic manner; and the participating scientists have widely varying opinions and perspectives on the nature of the problem and the meaning of the data. Some chapters focus on species, others on regions, and still others on parts of ecosystems. Some chapters are strictly empirical, whereas others are more synthetic or theoretical. Whaling was a human endeavor, ultimately driven by human needs and human behavior. The book's fifth and final section (Social Context) thus considers whaling from the perspectives of economics, policy, and law. The concluding chapter, by Peter Kareiva, Christopher Yuan-Farrell, and Casey O'Connor, is a retrospective view of what the other authors have written-how the question of whales and whaling has been addressed to this point, how it might be approached in the future, and how the various issues surrounding whales and ocean ecosystems compare with other problems in applied ecology and conservation biology.

This book reflects the collective wisdom of a group of people with a remarkable range of knowledge and perspective. My particular hope is that our efforts will stimulate others to think about how different today's oceans might be if the great whale fauna were still intact. In an increasingly dysfunctional world of nature, in which food web dynamics remain poorly known and grossly underappreciated, my greater hope is that our efforts will serve as a model for thinking about what conservationists and natural resource managers must do to restore and maintain ecologically effective populations of highly interactive species (Soulé et al. 2003)-one of the twenty-first century's most pressing needs and greatest challenges.

(Continues...)



Excerpted from Whales, Whaling, and Ocean Ecosystems by J.A. Estes Copyright © 2006 by Regents of the University of California. Excerpted by permission.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents


List of Contributors
List of Tables
List of Figures

1. Introduction

BACKGROUND
2. Whales, Interaction Webs, and Zero-Sum Ecology
3. Lessons From Land
4. When Ecological Pyramids Were Upside Down
5. Pelagic Ecosystem Response to a Century of Commercial Fishing and Whaling
6. Evidence for Bottom-Up Control of Upper-Trophic-Level Marine Populations

WHALES AND WHALING
7. Evolutionary Patterns in Cetacea
8. A Taxonomy of World Whaling
9. The History of Whales Read from DNA
10. Changes in Marine Mammal Biomass in the Bering Sea/Aleutian Islands and after the Period of Commercial Whaling
11. Industrial Whaling in the North Pacific Ocea 1952-1978
12. Worldwide Distribution and Abundance of Killer Whales
13. The Natural History and Ecology of Killer Whales
14. Killer Whales as Predators of Large Baleen Whales and Sperm Whales

PROCESS AND THEORY
15. Physiological and Ecological Consequences of Extreme Body Size in Whales
16. Ecosystem Impact of the Decline of Large Whales in the North Pacific
17. The Removal of Large Whales from the Southern Ocean
18. Great Whales as Prey
19. Whales and Whaling in the North
20. Legacy of Industrial Whaling
21. Predator Diet Breadth and Prey Population Dynamics
22. Bigger is Better

CASE STUDIES
23. Gray Whales in the Bering and Chukchi Seas
24. Whales, Whaling, and Ecosystems in the North Atlantic Ocean
25. Sperm Whales in Ocean
26. Ecosystem Effects of Fishing and Whaling in the North Pacific and Atlantic Oceans
27. Potential Influences of Whaling on the Status and Trends of Pinniped Populations

SOCIAL CONTEXT
28. The Dynamic Between Social Systems and Ocean Ecosystems
29. Whaling, Law, and Culture

OVERVIEW AND SYNTHESIS
30. Whales Are Big and It Matters
31. Restropection and Review

Index

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