The diet of the Antarctic Blue-eyed Shag Phalacrocorax atriceps bransfieldensis was analyzed based on the identification of the prey items in 50 regurgitated casts collected at Duthoit Point, Nelson Island, in February 1991. Benthic organisms, chiefly fish, were found to be the main components. 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 4 demersal-benthic species: Harpagifer antarcticus, Notothenia neglecta, Nototheniops nudifrons and Trematomus newnesi. For these populations in the study area, 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. The cephalopods beaks found in the samples indicate benthic octopods as the second group in importance behind fish. Other invertebrates such as polychaetes, gastropods, bivalves and crustaceans were occasional. The presence of algae and stones in the casts are also discussed and it is suggested that they were ingested accidentally. 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 item.
Abstract:
The use of Shag’s pellets as an appropriate technique to monitor the abundance of littoral fish populations is presented for consideration of the CCAMLR Ecosystem Monitoring Program Working Group. The effectiveness of the method is based on the very good agreement found between the fish species identified by the examinations of otoliths present in regurgitated cast and those regularly sampled with trammel-nets in the same area. Supporting literature for this proposal is also provided.
