FOOD OF EMPEROR PENGUINS (APTENODYTES-FORSTERI) IN THE WESTERN ROSS SEA, ANTARCTICA

The diet of the emperor penguin Aptenodytes forsteri in the western Ro ss Sea during spring was investigated by analysis of stomach contents sampled at three different localities. At Cape Washington, emperor pen guins 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 antar cticum (89% of the fish prey); the remainder of fish prey were mainly unidentified juveniles of different species of channichthyid fishes. T hree species dominated the crustacean part of the diet, i.e. the gamma rid amphipods Abyssorchomene rossi/plebs (30% of the crustacean prey) and Eusirus microps (22%), together with the euphausiid Euphausia crys tallorophias (24%). At Coulman Island and Cape Roget, fishes, mainly P . antarcticum, formed the bulk of the food (88 and 93% by mass, respec tively), crustaceans were minor prey (2.5 and 0.4%), and the squid Psy chroteuthis glacialis accounted for a small but significant part of th e food (3.5 and 0.8%). This study emphasizes the importance of the sma ll, shoaling pelagic fish Pleuragramma antarcticum as a key link betwe en zooplankton and top predators, including seabirds, in the food web and marine ecosystem of the Ross Sea.