FEEDING ECOLOGY AND INTERACTIONS OF TWO SPECIES OF SQUALOID SHARK: DEANIA CALCEUS (LOWE, 1839) AND ETMOPTERUS PRINCEPS (COLLETT, 1904) FROM THE ROCKALL TROUGH

Many species of deep-water shark are present in the Rockall Trough and are vulnerable to the impacts of deep-sea fisheries. Shark numbers are declining and commercially important prey items are being fished out of the ecosystem, affecting a number of aquatic food-webs. This paper describes the dietary composition of the birdbeak dogfish (Deania calceus) and the greater lantern shark (Etmopterus princeps) collected from the Rockall Trough between 55-57.6°N and 9- 14°W. D. calceus was collected from 650-1050 m at different locations and fed mainly on teleosts and cephalopods. Diet composition varied with depth but was not influenced by site, gender or maturity as immature specimens were largely absent from the sample. Comparisons of diet composition with previous fmdings demonstrate a shift in prey assemblage which may be as a result of fishing. E. princeps was sampled at 1500 m along the continental slope and diet composition was dominated by crustaceans, cephalopods and some fish. Diet composition was very different to that of D. calceus and did not vary between genders or maturity level. Both species exhibit generalist diets which counteract the effects of competition with other deep-water sharks and also the impacts of fisheries. Keywords: Competition, Deania calceus, Deep-sea fisheries, Depth, Diet, Etmopterus princeps, Gender, Maturity, Rockall TroughFaculty of Science, FRS, Aberdee