Temporal Variation in the Diet of the Gentoo Penguin Pygoscelis papua at Sub-Antarctic Marion Island

Abstract

The diet of the Gentoo Penguin Pygoscelis papua at sub-Antarctic Marion Island was sampled by stomach pumping at monthly intervals from March 1984 to March 1985. Overall, fish accounted for 53% of the diet by mass, crustaceans 44% and cephalopods 2%. Crustaceans predominated between March and June 1984; a marked increase in the proportion of fish in July coincided with the start of egg laying by Gentoo Penguins. Fish accounted for almost all of the diet in January and March 1985. Juvenile nototheniid fish, in particular Notothenia squamifrons, formed the bulk of the fish component; myctophids and Channichthys rhinoceratus were less common. The pelagic euphausiid Euphausia vallentini accounted for about 50% by mass of the overall crustacean component lumped over the entire study period. The decapod shrimp Nauticaris marionis was the most important crustacean species consumed during June to September 1984. Cephalopods, predominantly octopods, were taken mainly in February and March 1985. The hypothesis that seasonal changes in diet occur in direct response to the arrival of crested penguins (Eudyptes spp) early in summer is not supported by the data. Changes in diet appear to reflect local changes in the availability of prey species within the inshore waters exploited by Gentoo Penguins.