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Authors

Paul R. Wade, National Marine Mammal Laboratory, NOAA Fisheries, 7600 Sand PointWay NE, Seattle,Washington 98115, U.S.A.
Vladimir N. Burkanov, National Marine Mammal Laboratory, NOAA Fisheries, 7600 Sand PointWay NE, Seattle,Washington 98115, U.S.A.
Marilyn E. Dahlheim, National Marine Mammal Laboratory, NOAA Fisheries, 7600 Sand PointWay NE, Seattle,Washington 98115, U.S.A.
Nancy A. Friday, National Marine Mammal Laboratory, NOAA Fisheries, 7600 Sand PointWay NE, Seattle,Washington 98115, U.S.A.
Lowell W. Fritz, National Marine Mammal Laboratory, NOAA Fisheries, 7600 Sand PointWay NE, Seattle,Washington 98115, U.S.A.
Thomas R. Loughlin, National Marine Mammal Laboratory, NOAA Fisheries, 7600 Sand PointWay NE, Seattle,Washington 98115, U.S.A.
Sally A. Mizroch, National Marine Mammal Laboratory, NOAA Fisheries, 7600 Sand PointWay NE, Seattle,Washington 98115, U.S.A.
Marcia M. Muto, National Marine Mammal Laboratory, NOAA Fisheries, 7600 Sand PointWay NE, Seattle,Washington 98115, U.S.A.
Dale W. Rice, National Marine Mammal Laboratory, NOAA Fisheries, 7600 Sand PointWay NE, Seattle,Washington 98115, U.S.A.
Lance G. Barrett-Leonard, Vancouver Aquarium Marine Science Center, Vancouver, British Columbia V6B 3X8, Canada
Nancy Black, Monterey Bay Cetacean Project, P.O. Box 52001, Pacific Grove, California 93950, U.S.A.
Alexander Burdin, Alaska Sealife Center, 301 Railway Avenue, P.O. Box 1329, Seward, Alaska 99664, U.S.A.
John Calambokidis, Cascadia Research Collective, 218 1/2WFourth Avenue, Olympia,Washington 98501, U.S.A.Follow
Sal Cerchio, Molecular Systematics Lab, American Museum of Natural History, Central ParkWest at 79th Street, New York, New York 10024, U.S.A.
John K. B. Ford, Pacific Biological Station, Fisheries and Oceans Canada, 3190 Hammond Bay Road, Nanaimo, British Columbia V9T 6N7, Canada
Jeff Jacobsen, Department of Biological Sciences, Humboldt State University, Arcata, California
Craig Matkin, North Gulf Oceanic Society, 3430 Main Street, Suite B1, Homer, Alaska
Dena Matkin, North Gulf Oceanic Society, Gustavus, Alaska
Amee Mehta, Boston University Marine Program, Woods Hole, Massachusetts
Robert Small, Alaska Department of Fish and Game, 1255West 8th Street, P.O. Box 25526, Juneau, Alaska
Janice Straley, University of Alaska Southeast, Sitka, Alaska 99835, U.S.A.
Shannon McCluskey, Washington Cooperative Fish andWildlife Research Unit, School of Aquatic and Fishery Sciences, University ofWashington, Seattle,Washington 98195, U.S.A.
Glenn VanBlaricomm, Washington Cooperative Fish andWildlife Research Unit, School of Aquatic and Fishery Sciences, University ofWashington, Seattle,Washington 98195, U.S.A.
P J. ClaphamFollow

Date of this Version

2007

Comments

Published in MARINE MAMMAL SCIENCE, VOL. 23, NO. 4, 2007.

Abstract

Springer et al. (2003) contend that sequential declines occurred in North Pacific populations of harbor and fur seals, Steller sea lions, and sea otters. They hypothesize that these were due to increased predation by killer whales, when industrial whaling’s removal of large whales as a supposed primary food source precipitated a prey switch. Using a regional approach, we reexamined whale catch data, killer whale predation observations, and the current biomass and trends of potential prey, and found little support for the prey-switching hypothesis. Large whale biomass in the Bering Sea did not decline as much as suggested by Springer et al., and much of the reduction occurred 50–100 yr ago, well before the declines of pinnipeds and sea otters began; thus, the need to switch prey starting in the 1970s is doubtful. With the sole exception that the sea otter decline followed the decline of pinnipeds, the reported declines were not in fact sequential. Given this, it is unlikely that a sequential megafaunal collapse from whales to sea otters occurred. The spatial and temporal patterns of pinniped and sea otter population trends are more complex than Springer et al. suggest, and are often inconsistent with their hypothesis. Populations remained stable or increased in many areas, despite extensive historical whaling and high killer whale abundance. Furthermore, observed killer whale predation has largely involved pinnipeds and small cetaceans; there is little evidence that large whales were ever a major prey item in high latitudes. Small cetaceans (ignored by Springer et al.) were likely abundant throughout the period. Overall, we suggest that the Springer et al. hypothesis represents a misleading and simplistic view of events and trophic relationships within this complex marine ecosystem.

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