Comparative feeding ecology of two elasmobranch species, Squalus blainville and Scyliorhinus canicula, off the coast of Portugal

Abstract

The small-spotted catshark (Scyliorhinus canicula) (Linnaeus, 1758) and the longnose spurdog (Squalus blainville) (Risso, 1826) are two species occurring in the European and western African continental shelves with a wide geographical distribution. In this study, the diet ofS. blainville and S. canicula off the Portuguese western Atlantic coast was investigated in 2006 by collectingmonthly samples of these two species from local fishing vessels. In the stomachs of both species, crustaceansand teleosts were the dominant prey items, and molluscs, polychaetes, echinoderms, and sipunculids were found in lower abundance. In S. canicula, urochordate and chondrichthyan species were also observed in stomachs and were classified as accidental prey items. Scyliorhinus canicula consumed a broader group of prey items than didS. blainville. A significant diet overlap was observed, despite both species occupying different depth rangesover the continental shelf. Scyliorhinus canicula exhibited a consistency in diet composition among seasons, sexes, and maturity stages. Nonetheless, for both adults and juveniles,an increase in relative abundance of teleosts in the diet was observed in the spring and summer. This study provides evidence of the importance of S. canicula and S. blainville as benthic and pelagic predators along the western Atlantic coast.