Food of emperor penguins (Aptenodytes forsteri) in the western Ross Sea, Antarctica

The diet of the emperor penguin Aptenodytes forsteri in the western Ross Sea during spring was investigated by analysis of stomach contents sampled at three different 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 antarcticum (89% of the fish prey); the remainder of fish prey were mainly unidentified juveniles of different species of channichthyid fishes. Three species dominated the crustacean 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.