Understanding chinstrap penguin and elephant seal migrations in the Southern Ocean

Characterizing the high-latitude winter foraging habitats of migratory marine predators is necessary for conservation and management in Antarctica. Tracking data from chinstrap penguins ( Pygoscelis antarcticus ) and southern elephant seals ( Mirounga leonina ), key Antarctic predators with different diets and foraging habits, indicate that approximately 12% and 5%, respectively, of tagged penguins and seals undertake long-distance winter migrations to remote regions south of 60°S between 120°W and 170°W. Tracking data revealed reduced daily swimming speeds and two hotspots of increased use, consistent with increased foraging efforts, for both species in this region. Light limitation during winter, however, precludes the use of optical satellite data to characterize marine productivity here, but biogeochemical-Argo floats can provide year-round chlorophyll data. These data inform the Biogeochemical Southern Ocean State Estimate (B-SOSE), which provides year-round estimates of marine productivity. Overlapping the predator hotspots, B-SOSE predicts two areas with year-round elevated surface chlorophyll levels, consistent with previous studies indicating enhanced mixing in those areas. We hypothesize that persistent areas of elevated chlorophyll centered near 160°W and 120°W near the boundaries of the Ross Gyre and the southern boundary of the Antarctic circumpolar current support a productive food web capable of supporting the diverse foraging niches of pelagic species.