Diet composition and guild structure of mesopelagic and bathypelagic fishes near Macquarie Island, Australia

Abstract

Mesopelagic (200-1000 m) and bathypelagic (>1000 m) fish near Macquarie Island, Australia, are important in the diets of seals, seabirds, and Patagonian toothfish. They also form important links between the productivity at shallow and deeper water depths. Here we analyse the diets of 23 fish species, 13 of which are from the family Myctophidae from 254 stomach samples. Crustaceans (particularly copepods, amphipods, and euphausiids) were the dominant prey in 18 species. Fishes were the dominant prey in five species. Further analysis showed that five of the 13 myctophid fishes bad a low level of similarity in diet composition between individuals of each species, whereas the other eight species had significantly high levels of similarity. Cluster analysis and randomisation procedures suggested the existence of five trophic guilds among the Myctophidae.