Половозрастная структура группировки сивучей (Eumetopias jubatus) Командорских островов в 2008-2009 гг

Resighting data on Steller sea lion (Eumetopias jubatus, Schreber, 1776) branded as pup in the Commander Islands collected in 2008-2009 in the Northern Pacific. Analysis shows the age cohort of yearlings was the biggest among all age groups. The number of animals of age 2-3 years resighted during study period was considerably lower than number of yearlings and 4-5 year olds. After age 5 each following age cohort was decreasing in number than previous one. The number of animals older than 11-12 years old was extremely low. There was no any pattern of sex prevalence in juvenile age cohorts (younger than 4 years). In age groups of 4 years and older, with the exception of 6 and 7 years old, females were prevailing over males. The prevalence of females over males was greater in elder cohort (over 7 years) and increased with age. The current age and sex structure is may be responsible for sharp inter-annual changes in pup production of Steller sea lions breeding in the Commander Islands.