MARINE MAMMAL SCIENCE, 24(4): 845–863 (October 2008) C 2008 by the Society for Marine Mammalogy DOI: 10.1111/j.1748-7692.2008.00225.x Harbor seal population decline in the Aleutian Archipelago ROBERT J. SMALL Alaska Department of Fish and Game, Division of Wildlife Conservation, 1255 West 8th Street, Juneau, Alaska 99811, U.S.A. E-mail:
[email protected] PETER L. BOVENG National Marine Mammal Laboratory, NOAA/Alaska Fisheries Science Center, 7600 Sand Point Way NE, Seattle, Washington 98115, U.S.A. G. VERNON BYRD U.S. Fish and Wildlife Service, Alaska Maritime National Wildlife Refuge, 95 Sterling Hwy, Homer, Alaska 99603, U.S.A. DAVID E. WITHROW National Marine Mammal Laboratory, NOAA/Alaska Fisheries Science Center, 7600 Sand Point Way NE, Seattle, Washington 98115, U.S.A. ABSTRACT Populations of Steller sea lions, northern fur seals, and northern sea otters declined substantially during recent decades in the Bering Sea and Aleutian Islands region, yet the population status of harbor seals has not been assessed adequately. We de- termined that counts obtained during skiff-based surveys conducted in 1977–1982 represent the earliest estimate of harbor seal abundance throughout the Aleutian Islands. By comparing counts from 106 islands surveyed in 1977–1982 (8,601 seals) with counts from the same islands during a 1999 aerial survey (2,859 seals), we observed a 67% decline over the ∼20-yr period. Regionally, the largest decline of 86% was in the western Aleutians (n = 7 islands), followed by 66% in the central Aleutians (n = 64 islands), and 45% in the eastern Aleutians (n = 35 islands).