Diet Composition and Isotopic Analysis of Nine Important Fisheries Resources in the Eastern Adriatic Sea (Mediterranean)

We examined how the trophic ecology of nine economically important marine taxa varied across three distinct areas of the Adriatic Sea. These taxa included three species of demersal fishes (European hake Merluccius merluccius, red mullet Mullus barbatus, black-bellied angler Lophius budegassa) and two species of decapod crustaceans (Norway lobster Nephrops norvegicus, deep-water rose shrimp Parapenaeus longirostris) and four species of pelagic fishes (sardine Sardina pilchardus, anchovy Engraulis encrasicolus, Mediterranean horse mackerel Trachurus mediterraneus, Atlantic horse mackerel Trachurus trachurus). We used two complementary methods that differed in their temporal context to examine and compare diet. Stomach contents analysis was used to describe the short term diet while stable isotope analysis was used compare long-term assimilated diet. Results showed that although there were spatial differences in what each species consumed, and in their trophic and isotopic niches, each species fed at similar trophic position across locations, indicating similar ecological function. Comparisons of biomass-weighted trophic position (delta N-15) and consumer body size (log(2) mass) showed evidence for a common isotopic size spectrum across areas, indicating the existence of a size-structured food web. In turn this allowed us to provide a first estimate of the predator-prey body mass ratio (PPMR) for this area (655:1). Results obtained within this study, in future, could be used for ecological modeling and improved long-term management of the Adriatic Sea's marine resources.