Northern Sea Lion

Northern sea lions range along the North Pacific Ocean rim from northern Japan to California, with centers of abundance and distribution in the Gulf of Alaska and the Aleutian Islands, respectively. The species is not known to migrate, but individuals disperse widely outside of the breeding season (late May through early July), potentially intermixing with animals from other areas. Two separate stocks of Northern sea lions are recognized within U.S. waters: an eastern stock, which includes animals east of Cape Suckling, Alaska (that is, southeastern Alaska, British Columbia, Washington, Oregon, and California), and a western stock, which includes animals at and west of Cape Suckling (that is, the western Gulf of Alaska, the Aleutian Islands, and the Bering Sea).

In the 1960's, the worldwide population of Northern sea lions was about 250,000 adult and juvenile animals (nonpups) and was presumed to be healthy and stable. By the mid-1970's, the population in Alaska began to decline at about the same time as declines in other top predators were occurring. Subsequent declines reduced the worldwide population of Northern sea lions to 91,000 by 1989 (Loughlin et al. 1992). The current Northern sea lion population (including British Columbia) is estimated at 80,900 animals, with 43,200 in the western stock and 37,700 in the eastern stock.

The Alaska population of nonpups, which had numbered more than 157,000 animals in the 1970's, declined by 60% to less than 64,000 animals by 1989. Counts of sea lions from the Gulf of Alaska through the Aleutian Islands declined from 67,600 in 1985 to 18,700 in 1994, a decline of 72% in 9 years and more than 80% since the early 1970's. In some areas, such as the eastern Aleutian Islands, the decline was nearly 95%. The only area essentially unaffected by the decline has been southeast Alaska to northern California.

As a result of these population declines, the western stock of Northern sea lions was listed as an endangered species under provisions of the Endangered Species Act in 1990. The eastern stock was reclassified as threatened in 1996. The recovery outlook for the western stock is poor.