Winter foraging hotspots of Weddell seals (Leptonychotes weddellii) in the southern Weddell Sea

The region of the Filchner Outflow System (FOS) in the southeastern Weddell Sea is characterized by intensive and complex interactions of different water masses. These hydrographic features convert the FOS in an oceanographic hotspot, which may also show enhanced biological productivity and corresponding aggregations of marine top predators. In this context, six adult Weddell seals (Leptonychotes weddellii) were instrumented with CTD- combined satellite-relay dive loggers during austral summer 2014 to investigate the influence of environmental conditions on the seals’ foraging behaviour over winter and identify potential foraging hotspots in the FOS. Weddell seals preferred foraging in shallow areas of the continental shelf (< 700 m), where they presumably exploited the abundant bentho-pelagic fish fauna during both pelagic and demersal dives. Diurnal and seasonal variations in light availability also affected foraging activities. Furthermore, Eastern Shelf Water and modified Warm Deep Water were associated with increased hunting time and foraging effort. Moreover, two areas in the FOS were emphasized as potential foraging hotspots characterized by long residence times suggesting enhanced prey availability. However, the underlying biological principles contributing to these foraging hotspots still remain unclear. This highlights the importance of further ecological investigations as the FOS is already threatened by predicted climatic changes.