Diet of two icefish species from the South Shetland Islands and Elephant Island, Champsocephalus gunnari and Chaenocephalus aceratus 2001–2003

The summer diet of two species of icefishes (Channichthyidae) from the South Shetland Islands and Elephant Island, Champsocephalus gunnari and Chaenocephalus aceratus, was investigated from 2001 to 2003. C. gunnari fed almost exclusively on krill (Euphausia superba) in all years. The importance of other taxa (Themisto gaudichaudii, mysids, myctophids) in the diet was negligible. The average feeding rate of C. gunnari inferred from an exponential gastric evacuation model was between 1.0 and 1.5% body weight per day. Most of the stomachs of C. aceratus were empty. Stomachs with food contained mainly krill, mysids and fish. Among the fish taken, locally abundant species formed the bulk of the diet. They were Gobionotothen gibberifrons in 2001, Lepidonotothen larseni and C. gunnari in 2002 and L. larseni in 2003. An ontogenetic shift in feeding preference of C. aceratus was observed: Fish smaller than 30 cm fed on krill and mysids, while larger animals relied primarily on fish.