Steller Sea Lion Eumetopias jubatus in the Coastal Waters of the Chukotka Peninsula

Abstract

This article examines the current distribution of Steller sea lion Eumetopias jubatus in the coastal waters of the Chukotka Peninsula. The observations of animals were conducted, alongside studies of other marine mammal species, from observation posts located along the coast of the Chukotka in 1996 – 2000, 2001 – 05, 2010 – 15, and 2016 – 22. Since the second half of the 1990s there has been a gradual increase of Steller sea lions in the coastal waters. During the study years, the animals appeared annually in June before the breeding season, but until the end of September their numbers were not large (less than 0.03 per observation day). In October and November, sea lion numbers off the coast multiplied (to 0.20 per observation day). Based on these observations, we assume that, in recent years, at least 300 Steller sea lions have been coming to the coastal waters of the Chukotka Peninsula. The absence of observed animals tagged on the Asian coast and islands, and documentation of animals tagged in the Gulf of Alaska suggest that animals that breed in the eastern Aleutian Islands and the Gulf of Alaska have been entering, and continue to enter, the waters of the Chukotka Peninsula in the fall. The presence of Steller sea lions in the Chukchi Sea, at the northern extent of their current range, and their movement into the East Siberian Sea indicate that the northern border of the species’ distribution has shifted north. This shift is further supported by observations at Cape Chukotsky, near the northern boundary of the species’ range, where a haulout of Steller sea lions has increased in size over the past 20 years.