Feeding Habits and Biological Features of Deep-Sea Species of the Northwest Atlantic: Large-eyed Rabbitfish (Hydrolagus mirabilis), Narrownose Chimaera (Harriotta raleighana) and Black Dogfish (Centroscyllium fabricii)

Abstract

Feeding habits and biological features of three deep-water species -large-eyed rabbitfish (Hydrolagus mirabilis), narrownose chimaera (Harriotta raleighana) and black dogfish (Centroscyllium fabricii)- distributed in the Grand Bank and Flemish Cap (Northwest Atlantic) were analyzed. Both chimaeroid species fed on endo and epi-benthic organisms, but with different behavior. Narrownose chimaera showed a closer relationship with the sea bed in the feeding habits, denoted mainly by the high polychaete and sediment presence; while in large-eyed rabbitfish, the great importance of pelagic prey (Coryphaenoides rupestris and cephalopods) would indicate wider feeding habits, increased with the predator size. Black dogfish preyed mostly on pelagic and benthopelagic prey (crustaceans, scyphozoans and fish). High infestation of Gyrocotyle affected the chimaeroid species, increasing with depth. The parasitation affected 67% of large-eyed rabbitfish, with higher percentage for smaller individuals; narrownose chimaera (84% with parasites) had a greater number of parasites per host, and bigger individuals were more affected. However, presence of Gyrocotyle did not seem to harm the well-being of the specimens. Length-weight relationship indicated bigger body weight for males in the small sizes of 108, 31.5 and 50 cm of large-eyed rabbitfish, narrownose chimaera and black dogfish respectively. However, the body-eviscerated weigh relationship did not show differences between sexes. The hepatosomatic index (HIS) was high in all species, mainly in narrownose chimaera (31.3%) and it reached in the other species a value around the fourth part of their eviscerated weight. Black dogfish showed a clear increase of HSI with the body weight, while chimaerids presented a bigger variation