Establishing of local population, population dynamics and current abundance of Steller sea lion ( <i>Eumetopias jubatus</i>) in the Commander Islands

Abstract

The time course of the establishment of a local population of Steller sea lions in the Commander Islands, population dynamics and current abundance were studied using literature published since the 1930s and the author’s observations conducted during breeding seasons 2008-2011. The local population of Steller sea lions started formation in the early 1960s, when mature females first began to populate the islands and the population was fully established in the early 1990s. The whole process of development the Commander Islands Steller sea lion sub-population took about three decades. Abundance of adult and juvenile sea lions fluctuated highly in 1991-2011 without any statistically significant trend, but numbers of pups had a pronounced negative slope mostly due to three sharp declines in pup production in 2000, 2009, and 2011. A total of about 700 animals of age 1+ inhabit the islands during the breeding season and about 200 pups are born annually at the present time. This total number of Steller sea lions is close to the mean value for the period after 1990s. Nevertheless, occasional sharp declines in pup production cause some anxiety, so far as they could lead to extinction of the Steller sea lion sub-population in this area as had occurred in the middle of the 19th century.

Keywords

• сивуч
• командорские острова
• локальная популяция
• динамика численности
• современное состояние