Bering Sea | Mammals
Update on Steller sea lion abundance and trend on Yugo-Vostochny rookery, Medny Island, Russia, 2022 Presenter: Vladimir Burkanov , vladimir.burkanov@noaa.gov, Marine Mammal Laboratory, Alaska Fisheries Science Center Natasha Laskina , lask.natalia@gmail.com, Lomonosov Moscow State University Denis Gaev , denisgaev@live.ru, Marine Mammal Council Russel Andrews , russ@marecotel.org, Marine Ecology and Telemetry Research Thomas Gelatt , tom.gelatt@noaa.gov, Marine Mammal Laboratory, Alaska Fisheries Science Center Between June 4 - August 9, 2022 we completed 30 rookery-wide and 7 partial surveys of the Steller sea lion (SSL) rookery on Medny Island, Commander Islands, Russia. We used a DJI Mavic 2 PRO quadrocopter to collect aerial images of the entire rookery. The images were stitched into a georeferenced map using Agisoft Photoscan software and age-sex composition counts were conducted manually on a computer screen. During the pupping and mating season which lasts until July 10 a maximum of up to 292 SSL were observed on land. Maximum counts were 185 adult females, 54 adult males, 51 subadult males, and 13 juveniles. We counted 151 pups, five of which (3.3%) were born dead or died on the rookery during the field season. All of the age-sex groups declined relative to 2021 counts: non-pups by 8.8%, pups by 15.6%, females 5.6%, bulls 21.7%, subadult males 16,4%, and juveniles by 7.1%. The ten-year trend was near neutral with <1% decline for pups, non-pups, juveniles, and ~ 1.7% decline for bulls. The ten-year trend for females and subadult males was slightly positive. During the field season we recorded 70 branded SSL of which 68 were from Medny and two adult females were from Agattu Island in the Western Aleutians. Approximately 84% (37/44) Adult females had a pup. One of the marked adult females from Agattu Is immigrated from Agattu I. as a juvenile and has been seen to produce a pup every year since 2015. The other marked animal was 5 y.o. female which has also been observed on Medny every season since 2020, but never seen with a pup. This survey in 2022 indicates that the SSL population on Medny Is, the westernmost rookery in the Aleutian Chain, is fluctuating at the lowest level of the last decade with a slightly negative general trend.
Alaska Marine Science Symposium 2023 262
Made with FlippingBook flipbook maker