MEPS 661:229-242 (2021)  -  DOI: https://doi.org/10.3354/meps13609

ABSTRACT: Significant reductions in sea ice in the Pacific Arctic have occurred over the last 2 decades. Comparing the results of similarly conducted studies, but from different time periods, can increase our understanding of how marine mammals are responding to this change. We modeled the habitat selection and movement behavior of juvenile bearded seals Erignathus barbatus tagged with satellite transmitters in the Bering, Chukchi, and Beaufort seas during 2014-2018, a period of rapid decline in sea ice cover. We compared our results to an earlier study of juvenile bearded seals tagged in the Chukchi Sea during 2004-2009, a period of relatively stable sea ice coverage, and found differences. Seals in the earlier period strongly selected habitat near the ice edge and intermediate ice concentrations (50-60%) in both winter and spring. Seals in the later period strongly selected habitat away from the ice edge, showed no selection for any ice concentration in winter, and weakly selected low ice concentrations in spring (<50%). The likely explanation for these differences is changes in sea ice habitat because the shift away from the ice edge corresponds with a shift in the distribution of intermediate ice concentrations that seals prefer. During the later period, seals still used intermediate ice, which occurred farther from the ice edge and was now the average ice concentration available to them, masking any preference for intermediate ice in the habitat selection model. This change in sea ice conditions, although significant, may not currently be detrimental for juvenile bearded seals.

KEY WORDS: Pacific Arctic · Erignathus barbatus · Satellite telemetry · Habitat selection · State-space models · Climate change