The importance of the Patagonian Shelf for top predator species breeding at South Georgia

1. The rich zooplankton, fish and squid resources on the Patagonian Shelf sustain substantial populations of largely resident seabirds and marine mammals, These habitats are also visited seasonally by similar species from elsewhere but few data exist on their status and origin. Recent studies, using satellite-tracking to determine foraging ranges and feeding areas of seabirds and am marine mammals breeding at South Georgia, have shown that several species make substantial use of the waters of the Patagonian Shelf. 2. Wandering albatrosses use shelf-edge areas year-round with direct observations of both sexes of almost all age classes, including, breeding, pre-breeding and non-breeding individuals. White-chinned petrels and female Northern and Southern giant petrels mainly visit during incubation and post-breeding, particularly to the Falklands Current (White-chinned petrels) and to upwelling areas around the southern shelf-break from the Burdwood Bank in the cast to Staten Island and Diego Ramirez in the west (giant petrels). Northern giant petrel males during incubation and Antarctic fur seals in winter reach inner shelf habitats in the northern sector. In contrast, South Georgia populations of black-browed and grey-headed albatrosses do not appear to use the Patagonian Shelf at any stage of their breeding cycle. 3. Although the use of the Patagonian Shelf by visiting species is now best documented for South Georgia species, recent observational data confirm that seabirds from Diego Ramirez, Tristan da Cunha and Gough visit the southern and northern sectors, during both breeding and non-breeding seasons respectively. Several Antarctic species (notably Antarctic fulmar and cape petrel) winter in the region as do at least two albatross species from New Zealand; other species (especially Wilson's storm petrels) use it as a staging ground on migration, as do several species of baleen whales and possibly other cetacean species. 4. Three of the seabird species which breed on the Patagonian Shelf are Globally Threatened; seven of the visiting species (and four baleen whale species) also have this status. The Patagonian Shelf is, therefore, not only of global importance for the diversity and abundance of its resident top predators but is just as critical for the survival of many visiting species, some of which are even more endangered. 5. Combining data from satellite-tracking with conventional mapping from direct observations offers the prospect of defining the foraging ranges (and the main feeding areas within these) of a range of key top predator species. Such data should be used, in conjunction with similar information of the distributions of fish, squid and zooplankton resources and of fishing effort, to identify critical marine habitats whose precautionary, multiple-use sustainable management will be vital to protect the interests of both commercial fishers and top predators. Copyright (C) 2002 John Wiley Sons, Ltd.