Linking spatial distribution and feeding behavior of Atlantic horse mackerel (Trachurus trachurus) in the Strait of Sicily (Central Mediterranean Sea)

The Atlantic horse mackerel (Trachurus trachurus) is a semi-pelagic fish species with a wide geographical distribution and commonly found on the continental shelf. In recent years, the species has received someattention due to its ecological role in pelagic food webs. Stable isotope of nitrogen and carbon (?15N and ?13C) and Stomach Content Analysis (SCA) of T. trachuruswere adopted as tools to provide necessary knowledge on its feeding habits in the Strait of Sicily. The strong correlation found between ?15N and ?13C valueswith body length, together with significant ontogenetic shift evidenced by SCA, could be associated to changes in food availability,which in turn is triggered by environmental conditions. Spatial distribution of T. trachurus in the study area, mainly for small and mediumsize specimens, is linked to lower temperature, salinity and Photosynthetically Active Radiation (PARsat) valueswith higher aggregations on the Adventure Bank (i.e., an area characterized by periodic upwelling events). Larger size specimens mostly inhabited shallower waters characterized by higher temperature, salinity and PAR values, typical of the central-eastern part of the study area. Our results support the hypothesis that feeding behavior of T. trachurus is strictly linked to environmental factors (i.e. chiefly oceanographic conditions of the water column and day duration) that in turn influences the distribution of its prey. Findings can supply knowledge needed for improving fish stock management and promoting plans able to take into account also local ecosystem analysis.