Fish as diet of the blue-eyed shag, Phalacrocorax atriceps bransfieldensis at Half-Moon Island, South Shetland Islands

Thirty eight regurgitated casts collected in a colony at Half-moon Island, South Shetland Islands, during January and February 1993, were analyzed to determine the importance of fish in the diet of the blue-eyed shag Phalacrocorax atriceps bransfieldensis. Fish species were identified by means of otoliths found in the casts. The size and weight of the fish were estimated from the otolith lengths, using equations derived from data on local populations. Fish remains were present in all casts, comprising 91% of prey items. From the 937 otoliths found, 562 fish were represented and 524 were assigned to 5 demersal benthic species: Nototheniops nudifrons, Harpagifer antarcticus, Trematomus newnesi, Notothenia coriiceps and Gobionotothen gibberifrons. N. nudifrons was the most frequent (68.4%) and important by number (37.9%), whereas N. coriiceps prevailed in mass (35.8%). With the exception of G. gibberifrons, the fish species (and their size and age ranges) were identical to those found in a similar study at Duthoit Point, Nelson Island. However, the relative importance of the fish species in the diet differed between shags from the two areas.