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Marine Ecology Progress Series

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MEPS 673:211-227 (2021)  -  DOI: https://doi.org/10.3354/meps13787

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

W. C. Oosthuizen1,2,*, R. R. Reisinger3,4, M. N. Bester1, D. Steinhage5, H. Auel6, H. Flores5, R. Knust5, S. Ryan5,7, H. Bornemann5

1Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa
2Marine Apex Predator Research Unit, Institute for Coastal and Marine Research and Department of Zoology, Nelson Mandela University, Port Elizabeth 6031, South Africa
3Centre d’Etudes Biologiques de Chizé, UMR 7372 du CNRS-La Rochelle Université, 79360 Villiers-en-Bois, France
4Institute for Marine Sciences, University of California Santa Cruz, Santa Cruz, CA 95060, USA
5Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Am Handelshafen 12, 27570 Bremerhaven, Germany
6Universität Bremen, FB 02, Marine Zoology, PO Box 330 440, 28334 Bremen, Germany
7Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
*Corresponding author:

ABSTRACT: Climate variability and changes in sea ice dynamics have caused several ice-obligate 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.


KEY WORDS: Crabeater seal · Weddell seal · Filchner Trough · Euphausia superba · Pleuragramma antarctica · Density surface model · Distance sampling · Marine predator


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Cite this article as: Oosthuizen WC, Reisinger RR, Bester MN, Steinhage D and others (2021) Habitat-based density models of pack-ice seal distribution in the southern Weddell Sea, Antarctica. Mar Ecol Prog Ser 673:211-227. https://doi.org/10.3354/meps13787

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