Fish in the diet of the Antarctic shag at four colonies on the Danco Coast, Antarctic Peninsula

Abstract

The diet of breeding Antarctic shags (Phalacrocorax bransfieldensis) was investigated at four colonies on the Danco Coast, Antarctic Peninsula, by the analysis of 616 pellets (regurgitated casts) collected from December 1997 to February 1998. Overall, demersal-benthic fish were the most frequent and important prey at all the colonies, followed by octopods and gastropods. Amongst fish, Notothenia coriiceps was the main prey in all of the sampling sites, followed in similar importance by Gobionotothen gibberifrons at Cape Herschel, Primavera Island and Midas Island and in less importance by Harpagifer antarcticus at Py Point. There were marked differences among colonies in the size of the fish consumed. The largest and the smallest specimens were eaten by shags from Midas Island and Py Point respectively. This was mainly influenced by the number of specimens of the smallest fish species, H. antarcticus, consumed at Py Point. The differences in the diet composition may be related to the different foraging areas used by the shags. Results from this study differ from previous studies around the Antarctic Peninsula. The shags at the Danco Coast preyed markedly more intensively than those at the South Shetland Islands on G. gibberifrons. This finding reflects the low abundance of this fish species in inshore waters (< 100 m depth) at the South Shetland Islands and supports the use of the Antarctic shags to monitor trends in local populations of coastal fish species.