The diet of the South Georgia shag Phalacrocorax georgianus at South Orkney Islands in five consecutive

CASAUX R.,; RAMÓN A.

POLAR BIOLOGY

SPRINGER

Año: 2002 vol. 25 p. 557 - 561

0722-4060

The diet of the South Georgia shag Phalacrocorax georgianus at Laurie Island, SouthOrkney Islands, was studied by the analysis of 420 pellets (regurgitated casts) collected from the 1995to 1999 breeding seasons. Demersal-benthic fish were by far the main prey, followed by molluscs(mainly octopods and bivalves) and polychaetes. Harpagifer antarcticus (in 1995, 1998, 1999) andLepidonotothen nudifrons (1996, 1997) were the most frequent prey, followed by Gobionotothengibberifrons or Trematomus newnesi. H. antarcticus, followed by L. nudifrons or T. newnesi, was themost numerous prey in all of the seasons and predominated in mass in 1995 and 1996, followed byNotothenia coriiceps and L. nudifrons. In 1997 and 1999, G. gibberifrons and N. coriiceps were thespecies that most contributed to the diet whereas N. coriiceps and H. antarcticus contributed most in1998. Our results differ from those reported for the South Orkney Islands in previous studies. Thesedifferences could be due to the use of different diet-analysis methods and to shags-related and/orfisheries-related changes in the food availability around the colonies. These alternative explanationsare analysed and discussed.