Temporal variability and evaluation of methods used to infer diet of a Southern Ocean predator, the Adélie penguin Pygoscelis adeliae

Predicting ecosystem response to change and ensuring long-term sustainable management of Southern Ocean marine living resources is reliant upon ecosystem monitoring programmes that will provide data on key physical and biological components of the ecosystem and the functional relationships between these components. Integral to such monitoring programmes is accurate and reliable information on the diet of predators. In this study, I examined the long-term variability in the diet of Adélie penguins Pygoscelis adeliae, and their dependence on Antarctic krill Euphausia superba, the target of a large commercial fishery, to evaluate their effectiveness as an indicator species monitored to detect the effect of anthropogenic disturbance on the Southern Ocean ecosystem. Krill and fish were the dominant prey items in the diet of Adélie penguins from Béchervaise Island, however there was substantial inter- and intra-annual variation, as well as differences between sexes, in meal mass and diet composition. In years of low amounts of krill in the diet, reproductive performance declined, indicating Adélie penguins from this region are dependent on krill and could be considered an effective indicator species. However the large year-to-year variability naturally present in Adélie penguin diet limits the power to detect change due to an impact over short time periods (i.e.