The diet of the blue-eyed shag, Phalacrocorax atriceps bransfieldensis feeding in the Bransfield Strait

Abstract

The diet of the Antarctic blue-eyed shag Phalacrocorax atriceps bransfieldensis was analysed based on the identification of the prey items in 50 regurgitated casts collected at Duthoit Point, Nelson Island, in February 1991. Fish remains occurred in 100% of the casts and represented 68% by number and 90% by weight of the total prey items. From a total of 2112 otoliths found, 1176 fish specimens were identified belonging to four demersalbenthic species: Harpagifer antarcticus, Notothenia neglecta, Nototheniops nudifrons and Trematomus newnesi. Equations to estimate total length and weight from otolith length are provided. H. antarcticus and N. neglecta were the most frequent (92%) and important by weight (66%) respectively. Cephalopod beaks found indicate benthic octopods as the second group in importance after fish. Other invertebrates such as polychaetes, gastropods, bivalves and crustaceans were only occasional. The presence of algae and stones in the casts is attributed to accidental ingestion. Our results are in general agreement with those published for other Antarctic localities which indicate that P. atriceps is a benthic coastal feeder, with fish as its main food.