Feeding Ecology of Four Demersal Shark Species (Etmopterus spinax, Galeus melastomus, Scyliorhinus canicula and Squalus blainville) from the Eastern Aegean Sea

In this study, the diet composition and trophic ecology of four demersal chondrichthyan species; Etmopterus spinax, Galeus melastomus, Scyliorhinus canicula and Squalus blainville were studied in the eastern Aegean Sea. In the stomachs of the samples which mostly consisted of juvenile individuals, a total of 97 prey taxa were identified. Teleost fishes were the most important prey group. The diversity of stomach content ranged between 15 species in E. spinax. and 70 species in S. canicula. The dietary breadth of G. melastomus and S. canicula were found to be narrower than the other two species examined. In addition, high niche overlap scores were detected amongst the species. All of the examined species had trophic levels higher than 4; with the highest trophic level being 4.20 and belonging to E. spinax. Comparisons among calculated trophic levels by global methods and a regional weighted method, which is proposed in this study, showed that the regional method offers remarkable advantages that can be used to reduce the uncertainty of the estimations.