Adelie penguin foraging behaviour and krill abundance along the Wilkes and Adelie land coasts, Antarctica

contributed 19-37% to the penguins' diet and amphipods constituted 1-3%. (C) 2000 Elsevier Science Ltd. All rights reserved.The foraging behaviour of Adelie penguins Pygoscelis adeliae was studied simultaneously at Shirley Island (SI, 110 degrees E) and at Petrel Island (PI, 140 degrees E) in approximate conjunction with the ship-based krill survey conducted on board the RSV Aurora Australis. Acoustic and trawl data were collected near both study sites, albeit at the end of the penguins' breeding season. The distances travelled by Adelie penguins from Shirley Island were significantly greater than those travelled by penguins from Petrel Island (SI 31-144km; PI 6-79km). Mean foraging trip durations and mean maximal distances travelled were also significantly different between colonies (duration: SI guard 55 +/- 32 h, creche 113 +/- 17 h; PI guard 32 +/- 9 h, creche 25 +/- 7 h; distance: SI guard 182 +/- 135km, creche 353 +/- 93km; PI guard 100 +/- 142km, creche 86 +/- 28 km). All penguins foraged over the continental shelf or the shelf break and not in oceanic waters. The percentage distribution of dive depths was similar at both colonies; nearly 70% of all dives were to <35 m. Trawls from the ship contained krill Euphausia superba and E. crystallorophias near SI but only E. superba near PI. Biomass measurements showed that near SI 61% of krill biomass occurred at 63-97 m but the penguins dived to this depth range only 12% of their time; near PI 83% of the biomass was found from 43 to 63 m and 20% of dives reached these depths. The diet of the SI penguins consisted mainly of E. crystallorophias 51-53% by mass), while penguins from PI ingested large amounts of both euphausiids (27-38% E. superba, 27-39% E. crystallorophias). At SI, the remainder of the diet consisted of fish, mainly Pleuragramma antarcticum (26-30%), and amphipods ( ( 1%). Similarly, at PI, fishcontributed 19-37% to the penguins' diet and amphipods constituted 1-3%. (C) 2000 Elsevier Science Ltd. All rights reserved.