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Fishery Bulletin 103(2) 



habitat for sea otters, and at low densities it is possible 

 that these may be the only areas where they occur. 



We are reasonably confident that the 2000-01 sur- 

 veys yielded results that were comparable to baseline 

 surveys because the methods were closely repeated. The 

 difference in distribution of sea otter sighting zones 

 may have been a result of different aircraft configura- 

 tions. Although both aircraft were equipped with bubble 

 windows, the size and shape of these windows were 

 probably not identical. We accounted for any differences 

 by selecting the zones best suited to estimate sea otter 

 abundance for each survey period. In our data analysis, 

 we also accounted for the effects of survey conditions 

 (Beaufort sea state and viewing condition) in both data 

 sets. Our results indicate that in addition to changes in 

 sea otter abundance, distribution had changed markedly 

 between study periods as well. Because sea otter distri- 

 bution is currently concentrated closer to the coast, we 

 recommend revising the survey design for future popu- 

 lation surveys in this area. Rather than considering the 

 offshore area as a single survey stratum, it would be 

 more efficient to define nearshore and offshore survey 

 strata and allocate survey effort accordingly. 



To the west of the Alaska Peninsula study areas, 

 the sea otter population in the Aleutian archipelago 

 has declined to less than 10% of the estimated carry- 

 ing capacity (Burn et al., 2003). Further westward in 

 the Commander Islands, Russia, the sea otter popula- 

 tion appears to have remained stable over the same 

 time period (Burkanov and Burdin 9 ). To the east of 

 the Alaska Peninsula, sea otters have declined by an 

 estimated 569r in the nearby Kodiak archipelago since 

 1989 (Doroff et al. 10 ), but they appear to have remained 

 relatively stable in the areas of Cook Inlet and Kenai 

 Fiords (Bodkin et al. 11 ) According to the most recent 

 population surveys, the geographic extent of the sea ot- 

 ter decline does not appear to have exceeded the range 

 of the southwest Alaska population stock as described 

 by Gorbics and Bodkin (2001), where the overall decline 

 has been estimated at 56-68%. Because the cause of 

 the decline remains unknown, areas at the periphery 

 of the current decline should be regularly monitored 

 in the future. Given the close proximity between the 

 Aleutian Islands and the Commander Islands, Russia, 

 future research there may improve our understanding 

 of the cause of the decline in southwest Alaska. 



9 Burkanov, V. N., and A. M. Burdin. 2002. Distribution and 

 abundance of sea otter, steller sea lion, and killer whale in 

 the Commander Islands (Russia) during 2002. North Pacific 

 Wildlife Consulting, LLC Interim Report, 37 p. North 

 Pacific Wildlife Consulting , 12600 Elmore Rd., Anchorage, 

 AK 99516. 



10 Doroff, A. M., D. M. Burn, R. A. Stovall, and V. A. Gill. In 

 prep. Unexpected population declines of sea otters in the 

 Kodiak archipelago, Alaska. 



11 Bodkin, J. L. D. H. Monson, and G. E. Esslinger. 2003. A 

 report on the results of the 2002 Kenai Peninsula and Lower 

 Cook Inlet aerial sea otter survey, 10 p. U.S. Geological 

 Survey, Alaska Science Center Report. 1011 East Tudor 

 Road, Anchorage, Alaska 99503. 



The sea otter decline, which has occurred over a 

 broad geographic area, encompasses different habi- 

 tat types in southwest Alaska. The Aleutian Island 

 chain is primarily volcanic in origin and the majority 

 of habitat for foraging (waters <40 m) is concentrated 

 relatively near shore and is primarily a rocky substrate. 

 The Alaska Peninsula includes extensive soft-sediment 

 offshore habitat available to sea otters. Despite these 

 differences, the declines in sea otter populations are 

 similar between the Alaska Peninsula and the Aleutian 

 archipelago in both severity and time period, which may 

 imply a common cause. In addition to sea otters, severe 

 declines of harbor seals (Phoca vitulina), Steller sea 

 lions (Eumetopias jubatus), and fur seals (Callorhinus 

 ursinus) have also been documented within the same 

 general region, which suggests broader ecosystem-level 

 changes may be involved. Our survey results, along 

 with evidence of a declining sea otter population in the 

 Kodiak archipelago, prompted the U.S. Fish and Wild- 

 life Service to propose listing sea otters in southwest 

 Alaska as threatened under the U.S. Endangered Spe- 

 cies Act. The population decline in southwest Alaska is 

 one of the most significant conservation issues for the 

 sea otters in our time. 



Acknowledgments 



We thank the following individuals and organizations for 

 their contributions to 2000-01 surveys: Linda Comerci, 

 Thomas Evans, Susanne Kalxdorff, and Rosa Meehan 

 for their work as observers and data recorders during 

 survey operations; Ralph Aiken, Tom Blaesing, and Dave 

 Weintraub for their incomparable piloting skills; Izembek 

 National Wildlife Refuge manager Rick Poetter and his 

 staff for logistical support. Jay Brueggeman and Greg 

 Green provided the original 1986 aerial survey informa- 

 tion and assisted with data interpretation. We thank 

 John Haddix for assistance with GIS analysis of the 

 1986 survey data. We also thank James Bodkin, Verena 

 Gill, Mark Udevitz, and two anonymous reviewers for 

 comments on an earlier draft of this manuscript. 



Literature cited 



Burn, D. M., A. M. Doroff, and M. T. Tinker. 



2003. Carrying capacity and pre-decline abundance 



of sea otters (Enhydra lutris kenyoni) in the Aleutian 



Islands. Northwest. Nat. 84:145-148. 

 Doroff, A. M., J. A. Estes, M. T. Tinker, D. M. Burn, T J. Evans. 

 2003. Sea otter population declines in the Aleutian 



archipelago. J. Mammal. 84:55-64. 

 Estes, J. A. 



1977. Population estimates and feeding behavior of sea 



otters. In The environment of Amchitka Island, Alaska 



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S. Energy Resource and Development Administration, 



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 1990. Growth and equilibrium in sea otter populations. J. 



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