Temporal variation in the summer diet of Arctocephalus gazella at Stranger Point, Isla 25 de Mayo/King George, South Shetland Islands

Abstract

We report here the results of a comparative analysis on the diet of Antarctic fur seals, Arctocephalus gazella, between two different three year periods (triads) (1996–8 vs 2003–5), at Isla 25 de Mayo/King George Island, South Shetland Islands. The study was based on the collection and examination of 431 scats for the whole period. This is part of an ongoing long-term monitoring programme on the feeding habits of this otariid species in the area. In the 1990’s survey period, fish and krill were the most frequent prey taxa, occurring on average, in 82.9% and 78.8% of scats, respectively. In the 2000’s study period instead, the occurrence of krill (74%) largely surpassed that of fish (44%); the latter showing a negative trend through time. Overall, cephalopods and penguins were of minor relevance as prey of seals at this location with the exception of 1998 when penguins increased their relative contribution to the diet. More details on the taxonomic composition of the fish diet and the krill composition in terms of sex and maturity stage are reported. The possible influence of El Niño Southern Oscillation and Southern Annular Mode events on the temporal variation in the availability of different prey taxa to seals was analysed, though no clear pattern of association was found.