Adélie penguins foraging behaviour and krill abundance along the Wilkes and Adélie Land coasts, Antarctica

The foraging behaviour of Adélie Penguins Pygoscelis adeliae was studied simultaneously at Shirley Island (SI) near Casey Station and at Petrel Island (PI) at Dumont D'Urville during the 1995/96 breeding season. The study took place in conjunction with a ship-based krill survey in the CCAMLR Division 58.4.1 (south of 55 °S, 80 - 150 ° E) to determine the extent of overlap between penguin foraging areas and krill distribution. The maximal distances travelled by penguins from Shirley Island were significantly greater than those by penguins from Petrel Island (SI 68 - 113 km; Petrel Island about 37 km). Foraging trip durations and total distances travelled were also significantly different between colonies (duration: SI 55 - 113 h, PI 25 - 32 h; total distance: SI 182 - 352 km, PI 86 - 100 km). All penguins foraged over the continental shelf and not in oceanic waters. The percentage distribution of dive depths were similar at both colonies; nearly 70 % of all dives were to < 35 m. Trawls from the ship contained Euphausia superba and E. crystallorophias near Shirley Island but only E. superba near Petrel Island. The diet of the Shirley Island penguins consisted mainly of E. crystallorophias (47 - 51 %) while penguins from Petrel Island ingested large amounts of both euphausiids (27-38 % E. superba, 22 - 39 % E. crystallorophias). At Shirley Island, the remainder of the diet consisted of fish, mainly Pleuragramma antarcticum (20 - 40 %), and amphipods (< 3 %). The study took place in parallel to a ship-based krill survey in the CCAMLR Division 58.4.1 (south of 55 ° S, 80 - 150 ° E). Acoustic and trawl data were collected near both study sites, albeit at the end of the Adélie breeding season.