Fish in the diet of breeding Antarctic shags Phalacrocorax bransfieldensis at four colonies in the Danco Coast, Antarctic Peninsula

The diet of breeding Antarctic shags Phalacrocorax bransfieldensis was investigated at four colonies at 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 sampled, followed by octopods and gastropods. Among fish, Notothenia coriiceps was the main prey in all of the sampling sites, followed in similar importance by G. gibberifrons in Cape Herschel, Primavera Island and Midas Island and in less importance by H. antarcticus in Py Point. Between colonies there were marked differences in the size of the fish consumed. The largest specimens were eaten by shags from Midas Islands whereas the smallest ones by those from Py Point. This was mainly influenced by the number of specimens of the smallest fish species, H. antarcticus, consumed at this last colony. The differences in the composition of the diet may be related to the different foraging areas used by the shags. Our results differ from those presented in the only two previous studies on the diet of this shag at the Antarctic Peninsula. The shags at the Danco Coast preyed markedly more intensively on G. gibberifrons than those at the South Shetland Islands. This finding indicates a low abundance of this fish species in inshore waters (<100m depth) at the South Shetland Islands and support the use of the Antarctic Shag to monitor coastal fish populations.