The diet of Antarctic fur seals Arctocephalus gazella during the breeding season at Heard Island

Between September 1987 and February 1988, Antarctic fur seals Arctocephalus gazella at Heard Island fed mainly on fish with an average 95.2% of scats in monthly collections containing fish remains. Pelagic myctophids constituted more than 50% of fish taken by fur seals at the beginning of the summer season and again at the end when there was an influx of non-breeding male seals. During the middle period from October to December, fish from the surrounding shelf area comprised the bulk of the diet. These included various benthic nototheniid species, the bentho-pelagic ice fish Champsocephalus gunnari and skate (Bathyraja sp.), the latter being found in over 60%-of scats in October and November. The population of Antarctic fur seals at Heard Island is increasing at about the same rate as at South Georgia. There the increase is thought to be due to the high availability of krill E. superba, but, in the present study no euphausiid remains were found, so the increasing population at Heard Island has been supported on a local diet of fish. Whether this population increase can be sustained on a diet of fish is arguable. Trial fishing around Heard Island indicates that one of the major dietary items of the seals (C. gunnari) is of probable commercial importance and therefore any plans for the establishment of a fishery on Heard Island grounds must be considered in this light.