Aerial and ship-based surveys of Steller sea lions (Eumetopias jubatus) in southeast Alaska, the Gulf of Alaska, and Aleutian Islands during June and July 1991

Abstract

Aerial and ship-based surveys of Steller sea lions (Eumetopias jubatus) were conducted during June and July 1991 from Forrester Island in Southeast Alaska to Attu Island in the Aleutian Islands. A total of 36,459 adult and juvenile sea lions were counted at 103 trend sites in this area; this is 4.4% less than in 1990 (38,154) and represents a 68.8% decrease from 1979 (116,804). In the Kenai to Kiska index area, 21,737 sea lions were counted at trend sites, 4.5% less than in 1990 (22,754), and a 75.7% decrease from the 1970s count (89,364). In the past year, trend site numbers increased in Southeast Alaska (from 7,629 to 7,715), the eastern Aleutian Islands (from 3,801 to 4,231), and the western Aleutian Islands (from 2,327 to 2,411). Numbers decreased in the central Aleutian Islands (from 7,988 to 7,499). Decreases also occurred in the eastern (from 5,444 to 4,596), central (from 7,050 to 6,273), and western (from 3,915 to 3,734) Gulf of Alaska. Statistically significant declining trends in Alaskan adult and juvenile numbers have occurred since the late 1970s, except in the eastern Gulf of Alaska and Southeast Alaska, since 1985 in all of the Kenai to Kiska area except the eastern Aleutian Islands, and since 1989 in the central and eastern Gulf of Alaska. Differences between 1990 and 1991 were not statistically significant. From 1990 to 1991, pup numbers declined 13.1% at seven Kenai to Kiska rookeries (from 4,977 to 4,327) but increased 13.2% at four rookeries in Southeast Alaska and the eastern Gulf (from 4,258 to 4,821).


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