Mesoscale variability in the trophic ecology of the European hake Merluccius merluccius in the Strait of Sicily

The European hake Merluccius merluccius is one of the most important commercial species for the Mediterranean fisheries. In the Strait of Sicily, the species has some extended nursery areas, but its trophic ecology was not studied in detail, despite knowledge of the diet composition of fishes and their adaptability to food resource fluctuations is of major importance for the understanding of changes in fish abundance. In this study, we analyzed the trophic ecology of European hake by means of both stomach content and stable isotope analyses and correlated our results to environmental variables. According to both approaches, M. merluccius showed a clear ontogenetic shift in its diet with juveniles (70-160 mm total length (TL)) mostly relying on mysids and euphausiids, and adults (>160 mm TL) chiefly consuming larger prey, such as pelagic fish and decapods. Based on Spearman rank correlation (for isotopic tracers) and distance-based linear models (for diet), the trophic ecology of the species seemed to be mostly influenced by mesoscale variability of water masses in the Strait of Sicily, being latitude and longitude, temperature and salinity, among the most important explanatory variables. Further, fluorescence, as a proxy of primary production, was an explanatory variable likely enhancing zooplankton availability and in turn affecting M. merluccius diet.