Foraging behaviour of Weddell seals, and its ecological implications

Time-depth recorder data of eight adult Weddell seals (Leptonychotes weddel lii) provided simultaneous dive records over 8 days in the Drescher Inlet, eastern Weddell Sea coast, in February 1998. The seals primarily foraged wi thin two depth layers, these being from the sea surface to 160 m where temp erature and salinity varied considerably, and near the bottom from 340 to 4 50 m where temperature was lowest and salinity highest. While both pelagic and benthic diving occurred during daylight, the seals foraged almost exclu sively in the upper water column at night. Trawling during daytime confirme d that Pleuragramma antarcticum were by far the most abundant fish both in the pelagial and close to the bottom. Pelagic night hauls at 110-170 m dept h showed highly variable biomass of P. antarcticum. The temporal changes in the local abundance of P. antarcticum, particularly in the pelagial, may e xplain the trends in the seals' pelagic and benthic foraging activities. Th is study describes the Jaw movements of a hunting seal, which are presumabl y indicative of feeding events. Trophic links from the Weddell seal to fish , zooplankton and krill, Euphausia superba, are discussed.