Estimated food consumption by penguins at the Prince Edward Islands

Abstract

The consumption of food by the four species of breeding penguins at the Prince Edward Islands is assessed on an annual and seasonal basis. Total annual food consumption was estimated at 880 000 t, of which king penguins accounted for 74%, macaroni penguins 21%, rockhopper penguins 5% and gentoo penguins <1%. Pelagic fish, almost entirely myctophids, were the most important prey (70% of total prey biomass), followed by pelagic crustaceans (18%) and cephalopods (11%). Demersal fish and benthic crustaceans accounted for <1% of total consumption, being consumed only by gentoo penguins. Peak demands of between 2 and 3.3 × 106 kg d−1 occurred from October–December when three of the four species were breeding, including the two demi-populations of king penguins. Food demand decreased to 1.2 × 106 kg d−1 during winter when only king and gentoo penguins were present. Much of the prey are presumably captured within 300 km of the islands. Assuming an even distribution of foraging effort within their respective foraging ranges, rates of food transferred to penguins in November ranged from 4.1 × 10−3 g m−2 d−1 for macaroni penguins to 1.24 × 10−2 g m−2 d−1 for king penguins. In mid-July, transfer rates to king and gentoo penguins were 3.9 × 10−3 g m−2 d−1 and 6.7 × 10−3 g m−2 d−1, respectively. The importance of pelagic myctophid fish to penguin populations at the Prince Edward Islands is clear.