Risk of Marine Mammal Die-Offs in the Southern Ocean

Abstract

Compared to the vast amount of data on the northern polar and sub-polar marine mammals, there is relatively little information about the species in the Southern Ocean. These waters have been estimated to contain about 50% of the world’s seal population and 80% of the world’s biomass of pinnipeds (Laws 1984). Four species of seals – Weddell Leptonychotes weddellii, Ross Ommatophoca rossii, crabeater Lobodon carcinophagus, and leopard Hydrurga leptonyx – inhabit the pack-ice. In addition, the southern elephant seal Mirounga leonina and Antarctic fur seal Arctocephalus gazella, which breed farther to the north, forage southward into the marginal ice zone (Costa and Crocker 1996). Although these species are well adapted to the harsh polar environment, reproductive success depends on predictability of both ice conditions and food resources. Antarctic waters also are critical summer feeding grounds for many species of cetaceans, including six species of baleen whales and several species of odontocetes (Brown and Lockyer 1984; Costa and Crocker 1996; Moore et al. 1999).