Eating the neighbours: importance of small sharks in the diet of the rare deep-sea shark Dalatias licha

Abstract

Knowing the feeding habits of marine predators is essential to understanding their ecological role in the ecosystem. Such knowledge can also inform conservation strategies for threatened species. Research conducted on shark species inhabiting the deep sea is very scarce although these species may play a relevant role in the dynamics of the ecosystem. In the present study, we aimed to examine the feeding ecology (dietary composition and trophic level) of the kitefin shark (Dalatias licha), a deep-sea shark globally considered as Near Threatened and as Data Deficient in the Mediterranean Sea. In particular, by combining the use of stomach content and stable isotopic approaches, we aimed to examine the main feeding strategies of this marine predator at different temporal scales in the western Mediterranean Sea. The results revealed the clear importance of small sharks in the diet of the kitefin shark at different temporal scales, although fin-fish, crustaceans and cephalopods were also found to make up part of its diet. This feeding behaviour also indicates its position as an important predator within the food web of the western Mediterranean deep Sea. Our results provide direction for further studies on the role that predatory species play in Mediterranean food webs