Resource Partitioning among "Ancillary" Pelagic Fishes (Scomber spp., Trachurus spp.) in the Adriatic Sea

The Mediterranean is one of the most overfished seas of the world where mesopredators areseverely threatened. The trophic strategies of four pelagic species that inhabit the Adriatic Sea (Scomberspp. and Trachurus spp.) were investigated through an integrated approach of stomach contents andstable isotopes analyses. Our study demonstrated that Scomber colias feeds mainly on strictly pelagicprey, with fish larvae as a secondary prey in the Southern Adriatic Sea, while S. scombrus feeds onprey belonging to higher trophic levels. Smaller specimens of Trachurus mediterraneus have a dietmainly based on pelagic prey, while larger fishes rely on prey such as benthic decapods, showing anontogenetic shift in the diet of the species. Trachurus trachurus shows a preference for offshore anddeeper areas and a diet such as that of its congeneric, but no clear ontogenetic shift was observed.This spatial segregation allows the co-existence of these two species of Trachurus. Scomber coliasmainly inhabits southern areas and S. scombrus shows a preference for the northern sectors. Thislatitudinal gradient avoids the overlap of their trophic niches. Bayesian mixing models confirmedthat the trophic niches of these species only partially overlap in the middle of the trophic web.