FOOD-REQUIREMENTS OF BREEDING KING PENGUINS AT HEARD ISLAND AND POTENTIAL OVERLAP WITH COMMERCIAL FISHERIES

The diet composition of king penguins (Aptenodoytes patagonicus) at He ard Island (53 degrees 05'S; 73 degrees 30'E) was determined from stom ach contents of 98 adults captured as they returned to the island thro ughout 1992. During the two growth seasons, the diet was dominated by the myctophid fish Krefftichthys anderssoni (94% by number, 48% by mas s). The paralepidid fish Magnisudis prionosa contributed <1% by number s but 17% by mass. Mackerel icefish (Champsocephalus gunnari) accounte d for 17% by mass of chick diet in late winter, when chicks were malno urished and prone to starvation, although its annual contribution to t he penguins' diet was only 3%. Squid was consumed only between April a nd August; Martialia hyadesi was the commonest squid taken, comprising 40-48% of the winter diet. The remainder of the diet consisted of the squid Moroteuthis ingens and fish other than K. anderssoni. The energ y content of the diet mix fed to the chicks varied seasonally being hi ghest during the growth seasons (7.83 +/- 0.25 kJ g(-1)) and lowest in winter (6.58 +/- 0.19 kJ g(-1)). From energetic experiments we estima ted that an adult penguin consumed 300 kg of food each, of which its c hick received 55 kg during the 1992 season. The chicks received large meals at the beginning of winter (1.2 +/- 0.3 kg) and during the middl e of the second growth season (1.2 +/- 0.3 kg), and their smallest mea ls in late winter (0.4 +/- 0.1 kg). The gross energy required to rear a king penguin chick was estimated to be 724 MJ. The potential impact of commercial fisheries on the breeding activities of king penguins is discussed.