Steller Sea Lion (Eumetopias jubatus) at Tuleny Island, Russia in Autumn 2018: Abundance, Composition, and Entanglement.
The Steller sea lion (SSL, Eumetopias jubatus) inhabits the North Pacific Ocean off both the North American and Asian coasts. The abundance of the species in Asia declined by more than half in the second part of the 20th century. Decline recurred in the second decade of the 21th century after a short period of restoration. In contrast with the total dynamics of SSL in Asia, the reproductive aggregation on Tuleny I. (Sea of Okhotsk) has been growing almost continuously since the beginning of its formation in the late 1980s. Long-term monitoring of SSL at Tuleny I. always covered only summer reproductive seasons. We surveyed Tuleny I. in October 2018, and counted 1058 non-pup sea lions and 396 pups. The majority of tagged animals encountered at the rookery were of local origin. About one-third of the summer non-pup sea lions' number could remain at the rookery until the middle of October, which coincides with the seasonal appearance of sea lions off the coast of Japan. The sex-age structure was characterized by total absence of adult males and reduced proportion of subadult males and juveniles. It contrasts with autumn behavior of SSLs in the rookery of the northern Sea of Okhotsk. We observed that 0.7% of the inspected sea lions were entangled in marine debris. The proportion of entangled animals is lower in comparison with that of the whole population of Tuleny I. due to reduction in the ratios of males and juveniles, which entangle in foreign objects more often than adult females.
['Ryazanov|Sergey D|SD|', 'Permyakov|Peter A|PA|']
D000375:Aging D000818:Animals D005260:Female D062312:Islands D008297:Male D011156:Population Density D012426:Russia D046070:Sea Lions D014947:Wounds and Injuries
Steller sea lion entanglement Tuleny I. rookery autumn abundance group structure