Occurrence and group size of seals in the Western Antarctica: Results from the 2023 VII Turkish Antarctic Research Expedition

Antarctica offers a unique opportunity to study climate-related changes and ecological responses due to its remoteness and relatively undisturbed ecosystems. Pinnipeds, which are among the top predators in the Southern Ocean, are important bioindicators of environmental conditions. This study presents data on the distribution, species composition, and group sizes of pinnipeds observed during the VII Turkish Antarctic Research Expedition along the Western Antarctic Peninsula (WAP) in January–February 2023. The observations were conducted both from the research vessel BIO Hespérides and during land-based surveys at nine sites located in the islands off the Danco and Graham Coasts, at the north side of Marguerite Bay, in South Shetland Islands and Trinity Peninsula. A total of 70 sightings were recorded, including five pinniped species from the Phocidae and Otariidae families: southern elephant seals (Mirounga leonina), Weddell seals (Leptonychotes weddellii), leopard seals (Hydrurga leptonyx), crabeater seals (Lobodon carcinophaga), and Antarctic fur seals (Arctocephalus gazella). No Ross seals (Ommatophoca rossii) were sighted. Southern elephant seals sightings (n = 40) were the most frequently recorded, especially in the northern part of the study area, with one group comprising up to 250 individuals. Weddell seals (n = 16) were mostly sighted on the sea ice near Adelaide Island, while Antarctic fur seals (n = 8) were observed both on land and at sea, with one unusually large aggregation (approximately 1,000 individuals). Leopard seals (n = 3) and crabeater seals (n = 2) were observed in small numbers, mostly as solitary individuals or in small groups. These results contribute to the baseline knowledge of pinniped distribution patterns along the WAP and provide insights into regional population structures during the austral summer. The data are important for future ecological monitoring and understanding of species-specific responses to environmental changes in Antarctic ecosystems.