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Age- and sex-specific mortality and population structure in sea otters

Marine Mammal Science

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Abstract

We used 742 beach-cast carcasses to characterize age- and sex-specific sea otter mortality during the winter of 1990-1991 at Bering Island, Russia. We also examined 363 carcasses recovered after the 1989 grounding of the T/V Exxon Valdez, to characterize age and sex composition in the living western Prince William Sound (WPWS) sea otter population. At Bering Island, mortality was male-biased (81%), and 75% were adults. The WPWS population was female-biased (59%) and most animals were subadult (79% of the males and 45% of the females). In the decade prior to 1990-1991 we found increasing sea otter densities (particularly among males), declining prey resources, and declining weights in adult male sea otters at Bering Island. Our findings suggest the increased mortality at Bering Island in 1990-1991 was a density-dependent population response. We propose male-maintained breeding territories and exclusion of juvenile females by adult females, providing a mechanism for potentially moderating the effects of prey reductions on the female population. Increased adult male mortality at Bearing Island in 1990-1991 likely modified the sex and age class structure there toward that observed in Prince William Sound.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Age- and sex-specific mortality and population structure in sea otters
Series title:
Marine Mammal Science
Volume
16
Issue:
1
Year Published:
2000
Language:
English
Contributing office(s):
Alaska Biological Science Center
Description:
pp. 201-219
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Marine Mammal Science
First page:
201
Last page:
219
Number of Pages:
19