Habitat‐ based density models of pack-ice seal distribution in the southern Weddell Sea, Antarctica

• Published in: Marine Ecology Progress Series
• Main Authors: Oosthuizen, Wessel Christiaan, Reisinger, Ryan Rudolf, Bester, Marthan Nieuwoudt, Steinhage, D., Auel, H., Flores, H., Knust, R., Ryan, S., Bornemann, H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Inter Research 2022
• Subjects: Crabeater seal (Lobodon carcinophaga); Weddell seal (Leptonychotes weddelli); Filchner trough; Antarctic krill (Euphausia superba); Antarctic silverfish (Pleuragramma antarctica); Density surface model; Distance sampling; Marine predator; Antarctic; Austral; Filchner Trough; Hydrurga; Southern Ocean; The Antarctic; Weddell; Weddell Sea; Antarc*; Antarctic Krill; Antarctic silverfish; Antarctica; Crabeater Seal; Crabeater Seals; Euphausia superba; Hydrurga leptonyx; Leopard Seals; Leptonychotes weddelli; Sea ice; Weddell Seal; Weddell Seals
• Online Access: https://repository.up.ac.za/handle/2263/86047; https://doi.org/10.3354/meps13787

Climate variability and changes in sea ice dynamics have caused several iceobligate or krill-dependent populations of marine predators to decline, eliciting concern about their demographic persistence and the indirect ecological consequences that predator depletions may have on marine ecosystems. Pack-ice seals are dominant ice-obligate predators in the Antarctic marine ecosystem, but there is considerable uncertainty about their abundance and population trends. We modelled the density and distribution of pack-ice seals as a function of environmental covariates in the southern Weddell Sea, Antarctica. Our density surface modelling approach used data from aerial surveys of pack-ice seals collected in the 2013/14 austral summer. Crabeater seals Lobodon carcinophaga, the most numerous pack-ice seal we observed, occurred at the highest densities in areas with extensive sea ice near the continental shelf break, but were almost absent in areas of similar sea ice concentration in the southern extent of the Weddell Sea. The highest densities of Weddell seals Leptonychotes weddelli, which were less abundant than crabeater seals within the pack ice habitat, were predicted to occur over the continental shelf, near the shelf break. The distribution of both seal species broadly corresponded with the distribution and relative abundance of their main prey (Antarctic krill Euphausia superba and Antarctic silverfish Pleuragramma antarctica) obtained from concurrent ecosystem surveys. Ross seals Ommatophoca rossii and leopard seals Hydrurga leptonyx were not detected at all and are apparently rare within the southern Weddell Sea. These results can contribute to biodiversity assessments in the context of marine protected area planning in this region of the Southern Ocean. The Helmholtz Association Research Programme Polar regions And Coasts in the changing Earth System II (PACES II), Topic 1, WP 5 and WP 6, and is part of the Helmholtz Association Young Investigators Groups Iceflux: Ice-ecosystem carbon flux in polar oceans ...