BIOLOGIYA MORYA, 2014, Vol. 40, No. 6, pp. 449-454

Reproductive success of Steller sea lion Eumetopias jubatus (Schreber, 1776) on Brat Chirpoev and Medny Islands in the years 2001-2011

© 2014 P. A. Permyakov¹, S. D. Ryazanov^1,2, A. M. Trukhin¹, E. G. Mamaev³, V. N. Burkanov^2,4

¹V.I. Ilyichev Pacific Oceanological Institute, Far East Branch, Russian Academy of Sciences, Vladivostok 690041;
²Kamchatka Filial of the Pacific Institute of Geography, Far East Branch, Russian Academy of Sciences, Petropavlovsk-Kamchatski 683083;
³Komandorski State Nature Biosphere Reserve, Nikolskoe 684500;
⁴National Marine Mammal Laboratory, AFSC, NMFS, Seattle, WA98115, USA

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The reproductive success of Steller sea lion was estimated based on monitoring the breeding performance of known-age branded females on Brat Chirpoev and Medny islands in 2001-2011. First pup birth occurred at 4 years of age, but the majority of females gave birth to their first pup at the age of 5 years on both islands. The period of the highest realization of female initial reproductive capacity on Medny Island was 4-5 years shorter, compared to Brat Chirpoev Island. The differences were caused by a lower number of middle-aged females and a higher proportion of non-pregnant females on Medny Island. The low reproductive success of females is probably the main reason of depression of the Steller sea lion population on Medny Island.

Key words: Steller sea lion, Commander Islands, Kuril Islands, reproductive success.