Seasonal Trophic Ecology and Diet Shift in the Common Sole Solea solea in the Central Adriatic Sea

The common sole is one of the most important commercial fish species landed in Europe. In this study, we analysed the trophic ecology of this species at the seasonal scale, coupled with data on its condition (by hepatosomatic and gonadosomatic indices). We observed significant seasonal changes in diet, clearly linked to the reproductive cycle only for females. Both the analysis based on stomach contents and on stable isotopes highlighted a greater contribution of prey of high energetic content before the spawning period, notwithstanding the opportunistic behaviour of this benthophagous species. The common sole, Solea solea, is one the most important commercial species in Europe and, within the Mediterranean, the Adriatic basin is the most crucial area for its production. Although the species is overexploited in the basin, data on its trophic ecology are fragmentary, even though this is one of the most important features within the Ecosystem Approach to Fishery. Here, we analysed temporal variations in the feeding ecology of the species by using an integrated approach of stomach contents and stable isotope analyses coupled with the analysis of some condition indices such as the gonadosomatic and the hepatosomatic indices. Changes in diet and trophic level across the years in adult females were clearly linked to the different energetic requirements facing reproduction. Temporal changes throughout the year were mainly related to changes in food availability. This study confirms the opportunistic behaviour of this benthophagous species and its role as a mesopredator, opening new perspectives for further investigations on the effects of the overexploitation of this important fishery resource on the marine trophic web.