Hindell, Mark A; Lydersen, Christian; Hop, Haakon; Kovacs, Kit Maureen (2012): (Table 1) Stable carbon and nitrogen isotopic ratios of potential prey species of bearded seals (Erignathus barbatus), Svalbard [dataset]. PANGAEA, https://doi.org/10.1594/PANGAEA.811213,

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Supplement to: Hindell, MA et al. (2012): Pre-Partum Diet of Adult Female Bearded Seals in Years of Contrasting Ice Conditions. PLoS ONE, 7(5), e38307, https://doi.org/10.1371/journal.pone.0038307

Changing patterns of sea-ice distribution and extent have measurable effects on polar marine systems. Beyond the obvious impacts of key-habitat loss, it is unclear how such changes will influence ice-associated marine mammals in part because of the logistical difficulties of studying foraging behaviour or other aspects of the ecology of large, mobile animals at sea during the polar winter. This study investigated the diet of pregnant bearded seals (Erignathus barbatus) during three spring breeding periods (2005, 2006 and 2007) with markedly contrasting ice conditions in Svalbard using stable isotopes (d13C and d15N) measured in whiskers collected from their newborn pups. The d15N values in the whiskers of individual seals ranged from 11.95 to 17.45 per mil, spanning almost 2 full trophic levels. Some seals were clearly dietary specialists, despite the species being characterised overall as a generalist predator. This may buffer bearded seal populations from the changes in prey distributions lower in the marine food web which seems to accompany continued changes in temperature and ice cover. Comparisons with isotopic signatures of known prey, suggested that benthic gastropods and decapods were the most common prey. Bayesian isotopic mixing models indicated that diet varied considerably among years. In the year with most fast-ice (2005), the seals had the greatest proportion of pelagic fish and lowest benthic invertebrate content, and during the year with the least ice (2006), the seals ate more benthic invertebrates and less pelagic fish. This suggests that the seals fed further offshore in years with greater ice cover, but moved in to the fjords when ice-cover was minimal, giving them access to different types of prey. Long-term trends of sea ice decline, earlier ice melt, and increased water temperatures in the Arctic are likely to have ecosystem-wide effects, including impacts on the forage bases of pagophilic seals.

Prey species were obtained in Kongsfjorden with trawling (fishes) or by SCUBA diving during the open water season from late April to early September, in 1997 and 2006. Data extracted in the frame of a joint ICSTI/PANGAEA IPY effort, see http://doi.pangaea.de/10.1594/PANGAEA.150150