Population surveys of Steller sea lions in the Kuril Islands in 1995 and 1996

Abstract

Cooperative surveys by Russian and Japanese scientists were conducted on the status of Steller sea lion Eumetopias jubatus in the Kuril Islands in 1995, and American scientists joined in this project in 1996. In 1995, a total of 1,541 pups and 2,652 non-pups were counted at four of the five surveyed rookeries, Antsiferova Island, Raykoke Island, Lovushki Rocks, Srednego Island, and Chernyye Brat'ya Island, and in 1996 a total of 954 pups and 1,730 non-pups were counted at three rookeries. A total of 701 pups were tagged and branded on seven occasions at five rookeries. Pup mortality was estimated to be between 2.6% and 7.1%, based on the counts of live and dead pups on the days of tagging and branding. On Raykoke Island, the branded pups may be different in mortality from non-branded ones. Seven debris-entangled sea lions were found in 1995, but no entangled sea lions were found in 1996. One tagged or branded male and 11 females were re-sighted on Srednego Island, 29 females on Raykoke Island, 4 females on Antsiferova Island, one male each on Shiashkotan and Onekotan Islands. Multiple observations of the marked sea lions suggest that they travel widely in the Okhotsk Sea, the Japan Sea, and the North Pacific.