| Autor: |
Altukhov AV; University of Alaska Fairbanks, Fairbanks, Alaska, USA; Kamchatka Branch of the Pacific Geographical Institute FEB RAS, Petropavlovsk-Kamchatsky, Kamchatsky Kray, Russia., Andrews RD; University of Alaska Fairbanks, Fairbanks, Alaska, USA; Alaska SeaLife Center, Seward, Alaska, USA., Calkins DG; North Pacific Wildlife Consulting LLC, Anchorage, Alaska, USA., Gelatt TS; National Marine Mammal Laboratory (AFSC, NMFS, NOAA), Seattle, Washington, USA., Gurarie ED; Department of Biology, University of Maryland, College Park, Maryland, USA; School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, USA., Loughlin TR; TRL Wildlife Consulting (NMML retired), Seattle, Washington, USA., Mamaev EG; State Nature Reserve 'Komandorsky', Nikolskoe, Kamchatsky Kray, Russia., Nikulin VS; Kamchatka Research Institute of Fisheries and Oceanography, Petropavlovsk-Kamchatsky, Kamchatsky Kray, Russia., Permyakov PA; V.I.Il'ichev Pacific Oceanological Institute FEB RAS, Vladivostok, Primorsky Kray, Russia., Ryazanov SD; Kamchatka Branch of the Pacific Geographical Institute FEB RAS, Petropavlovsk-Kamchatsky, Kamchatsky Kray, Russia; V.I.Il'ichev Pacific Oceanological Institute FEB RAS, Vladivostok, Primorsky Kray, Russia., Vertyankin VV; Kronotsky Reserve, Yelizovo, Kamchatsky Kray, Russia., Burkanov VN; Kamchatka Branch of the Pacific Geographical Institute FEB RAS, Petropavlovsk-Kamchatsky, Kamchatsky Kray, Russia; North Pacific Wildlife Consulting LLC, Anchorage, Alaska, USA; National Marine Mammal Laboratory (AFSC, NMFS, NOAA), Seattle, Washington, USA. |
| Abstrakt: |
After a dramatic population decline, Steller sea lions have begun to recover throughout most of their range. However, Steller sea lions in the Western Aleutians and Commander Islands are continuing to decline. Comparing survival rates between regions with different population trends may provide insights into the factors driving the dynamics, but published data on vital rates have been extremely scarce, especially in regions where the populations are still declining. Fortunately, an unprecedented dataset of marked Steller sea lions at rookeries in the Russian Far East is available, allowing us to determine age and sex specific survival in sea lions up to 22 years old. We focused on survival rates in three areas in the Russian range with differing population trends: the Commander Islands (Medny Island rookery), Eastern Kamchatka (Kozlov Cape rookery) and the Kuril Islands (four rookeries). Survival rates differed between these three regions, though not necessarily as predicted by population trends. Pup survival was higher where the populations were declining (Medny Island) or not recovering (Kozlov Cape) than in all Kuril Island rookeries. The lowest adult (> 3 years old) female survival was found on Medny Island and this may be responsible for the continued population decline there. However, the highest adult survival was found at Kozlov Cape, not in the Kuril Islands where the population is increasing, so we suggest that differences in birth rates might be an important driver of these divergent population trends. High pup survival on the Commander Islands and Kamchatka Coast may be a consequence of less frequent (e.g. biennial) reproduction there, which may permit females that skip birth years to invest more in their offspring, leading to higher pup survival, but this hypothesis awaits measurement of birth rates in these areas. |
