Bering Sea | Mammals
Spotted seal abundance and size composition at terrestrial haulouts in western Bering Sea Presenter: Irina Trukhanova , irina_trukhanova@yahoo.com, North Pacific Wildlife Consulting LLC Vladimir Burkanov , VBurkanov@gmail.com, National Marine Mammal Laboratory, AFSC, NMFS, NOAA, Seattle, USA; Kamchatka Branch of the Pacific G
Diana Smolina , smolka2628@gmail.com, St Petersburg State University Alexey Altukhov , aaltukhov@gmail.com, North Pacific Wildlife Consulting
Spotted seal ( Phoca largha ) population in the Bering Sea is considered to be affected by recent low-ice years leading to changes in abundance, distribution, and habitat use, increased mortality rates and major reproductive failures. Abundance and age structure of spotted seal groups occupying terrestrial haulouts during the open water season might reflect the overall population status. We carried out a series of UAV-based surveys of spotted seal coastal haulouts between July 21 and July 29, 2021 on East coast Kamchatka, Karaginsky Gulf, Western Bering Sea. 20 haulout sites were surveyed with a total of 69 flights performed. The flights were carried out between 20 and 140 m above the sea level taking into account weather conditions and seal reaction to the presence of UAV. UAVs collected high-resolution georeferenced haulout imagery which was processed and stitched into orthomosaics using Agisoft Metashape software. We obtained comprehensive spotted seal counts for the surveyed haulouts on East coast Kamchatka and estimated size composition of the spotted seal haulout groups. The sum of maximum obtained counts across all surveyed sites was 4042 individual seals. Seal body length measurement including the hind flippers ranged between 0.82 and 1.99 m with the mean of 1.51 (SD=0.209) m. This suggested that both juvenile and adult animals were present at the haulout sites during the survey period. We derived the age composition of the groups using the historical size-age relationship in harvested seals as reference. Here we are presenting the preliminary results of the project, while additional field data collection is anticipated in the near future. The project results will be compared to available historical records and analyzed in the light of current environmental conditions. The project is supported by the North Pacific Research Board grant.
Alaska Marine Science Symposium 2023 56
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