Trophic ecology of the deep-sea skate Dipturus oxyrinchus (Linnaeus, 1758) in the bathyal food web of the central Mediterranean Sea

The Mediterranean Sea is a biodiversity hotspot where most elasmobranchs are severely threatened, with poor knowledge about life history traits and trophic ecology. In this context, our study focused on the trophic ecology of the deep-sea longnose skate (Dipturus oxyrinchus) in the Strait of Sicily (central Mediterranean), designated as an Important Shark and Ray Area. The objectives of the present study were to investigate the main changes in the feeding habits of the species according to ontogeny and bathymetric distribution. We collected 152 specimens from the continental slope (200-750 m) from 2016 to 2019. The combination of stomach content and stable isotope analyses identified the longnose skate as a generalist feeder, with a diet dominated by crustaceans, with smaller contributions from bony fish and cephalopods. Among crustaceans the most consumed were decapods (including Parapenaeus longirostris, Iridonida speciosa, Chlorotocus crassicornis) and mysids (Lophogaster typicus). Generalized additive models indicated that predator body size and depth had a significant effect on the consumption pattern of certain prey groups. Significant ontogenetic changes were observed, with smaller individuals primarily preying upon benthic organisms and larger individuals adopting a more benthopelagic diet, reflected by a slight increase in trophic position.