Trophic structure of pelagic species in the northwestern Mediterranean Sea

• We analyzed the trophic interactions of 11 pelagic species in the NW Mediterranean Sea.
• Sardina pilchardus and Engraulis encrasicolus partially overlap their isotopic niches.
• Species within the genera Trachurus spp. and Scomber spp. had segregated isotopic niches.
• Squids, Illex coindetii and Loligo vulgaris had different trophic positions.
• Overall community trophic structure appeared relatively stable through the year.

Ecological knowledge of food web interactions within pelagic marine communities is often limited, impairing our capabilities to manage these ecologically and economically important marine fish species. Here we used stable isotope analyses to investigate trophic interactions in the pelagic ecosystem of the northwestern Mediterranean Sea during 2012 and 2013. Our results suggest that European sardine, Sardina pilchardus, and anchovy, Engraulis encrasicolus, are consumers located at relatively low levels of the pelagic food web. Unexpectedly, the round sardinella, Sardinella aurita, appeared to be located at a higher trophic level than the other small pelagic fish species, although previous studies found similarity in their diets. Isotope data suggested that trophic niches of species within the genera Trachurus spp. and Scomber spp., were distinct. Atlantic bonito Sarda sarda, European hake Merluccius merluccius and European squid Loligo vulgaris, appeared to feed at higher trophic levels than other species. Despite some intraspecific seasonal variability for some species, community trophic structure appeared relatively stable through the year. These data provide an important step for developing models of food web dynamics in the northwestern Mediterranean Sea.