Food of emperor penguins (Aptenodytes forsteri)

Abstract The diet of the emperor penguin Aptenodytes forsteri in the western Ross Sea during spring was in-vestigated by analysis of stomach contents sampled at three dierent localities. At Cape Washington, emperor penguins feeding chicks consistently preyed on fishes (89 to 95 % by mass) and crustaceans (5 to 11%) over the four spring seasons examined. By far the commonest prey was the Antarctic silverfish Pleuragramma antarc-ticum (89 % of the fish prey); the remainder of fish prey were mainly unidentified juveniles of dierent species of channichthyid fishes. Three species dominated the crus-tacean part of the diet, i.e. the gammarid amphipods Abyssorchomene rossi/plebs (30 % of the crustacean prey) and Eusirus microps (22%), together with the euphausiid Euphausia crystallorophias (24%). At Coulman Island and Cape Roget, fishes, mainly P. antarcticum, formed the bulk of the food (88 and 93 % by mass, respectively), crustaceans were minor prey (2.5 and 0.4%), and the squid Psychroteuthis glacialis accounted for a small but significant part of the food (3.5 and 0.8%). This study emphasizes the importance of the small, shoaling pelagic fish Pleuragramma antarcticum as a key link between zooplankton and top predators, including seabirds, in the food web and marine ecosystem of the Ross Sea