Bering Sea | Mammals
Brief results of Northern fur seal pup survey on Yugo-Vostochny and Urilie rookeries, Medny Island, Commander Islands, 2021-2022 Presenter: Natasha Laskina , lask.natalia@gmail.com, Lomonosov Moscow State University Denis Gaev , denisgaev@live.ru, Marine Mammal Council Vladimir Burkanov , VBurkanov@gmail.com, National Marine Mammal Laboratory, AFSC, NMFS, NOAA Thomas Gelatt , tom.gelatt@noaa.gov, Marine Mammal Laboratory, Alaska Fisheries Science Center In the summers of 2021 and 2022 we completed multiple counts of two of the four northern fur seal (NFS) rookeries on the Commander Islands, Russia. We used DJI drones Phantom 4 PRO and Mavic 2 PRO to obtain aerial images of the entire rookeries, stitched them using Agisoft Photoscan software and counted pups manually on the computer screen. In 2021 we conducted pup surveys on July 28 and 29 on the two rookeries located on Medny Island. The maximum count of pup on Yugo-Vostochny rookery was 17,567 alive (mean 17,325±242) and 276 (mean 264±12) dead; on Urilie rookery we counted 6,699 alive (mean 6,385±314) and 66 (mean 65±1) dead. In 2022 we completed four counts on Yugo-Vostochny between July 31 - August 9. We counted a maximum of 20,459 alive (mean 19,642±555) and 364 (mean 337±12) dead pups. We completed two surveys of Urilie rookery on July 27 and 28, 2022 and counted a maximum of 7,314 alive (mean 7,303±12) and 133 (mean 132±2) dead pups. The count deviation for live pups between surveys within one season ranged from 0.2% to 12.9%. The yearly changes indicated a 16.5% increase for Yugo-Vostochny and a 9.2% increase for Urilie. Due to the large variation within season counts we assumed that the difference was more attributable to count variation than a real increase in pup production. The dead pup number on both rookeries and all surveys ranged 0.9- 1.8% which was extremely low compared to ground counts (usually 8-12%). So, we think there is a large undercount of dead pups using aerial imagery survey method. The number of live pups was close to the count obtained with ground counts conducted on both rookeries in 2007 (Yugo-Vostochnoe rookery: 18,700 pups, Urulie rookery: 7,300 pups). Thus, we conclude that the NFS pup production on these two rookeries of Medny Island have varied little since 2007 and the population is stable.
Alaska Marine Science Symposium 2023 265
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