NDLI: Inter-decadal patterns of population and dietary change in sea otters at Amchitka Island, Alaska

Content Provider	Springer Nature Link
Author	Watt, J. Siniff, D. B. Estes, J. A.
Copyright Year	2000
Abstract	After having been hunted to near-extinction in the Pacific maritime fur trade, the sea otter population at Amchitka Island, Alaska increased from very low numbers in the early 1900s to near equilibrium density by the 1940s. The population persisted at or near equilibrium through the 1980s, but declined sharply in the 1990s in apparent response to increased killer whale predation. Sea otter diet and foraging behavior were studied at Amchitka from August 1992 to March 1994 and the data compared with similar information obtained during several earlier periods. In contrast with dietary patterns in the 1960s and 1970s, when the sea otter population was at or near equilibrium density and kelp-forest fishes were the dietary mainstay, these fishes were rarely eaten in the 1990s. Benthic invertebrates, particularly sea urchins, dominated the otter’s diet from early summer to mid-winter, then decreased in importance during late winter and spring when numerous Pacific smooth lumpsuckers (a large and easily captured oceanic fish) were eaten. The occurrence of spawning lumpsuckers in coastal waters apparently is episodic on a scale of years to decades. The otters’ recent dietary shift away from kelp-forest fishes is probably a response to the increased availability of lumpsuckers and sea urchins (both high-preference prey). Additionally, increased urchin densities have reduced kelp beds, thus further reducing the availability of kelp-forest fishes. Our findings suggest that dietary patterns reflect changes in population status and show how an ecosystem normally under top-down control and limited by coastal zone processes can be significantly perturbed by exogenous events.
Starting Page	289
Ending Page	298
Page Count	10
File Format	PDF
ISSN	00298549
Journal	Oecologia
Volume Number	124
Issue Number	2
e-ISSN	14321939
Language	English
Publisher	Springer-Verlag
Publisher Date	2000-08-04
Publisher Place	Berlin, Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Content Type	Text
Resource Type	Article
Subject	Ecology, Evolution, Behavior and Systematics

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