Assessing the effects of trawling disturbance on the diet of red mullet, Mullus barbatus barbatus (L. 1758), in the Southern Tyrrhenian Sea

ABSTRACT: Trawling activities generate numerous consequences including changes in the ecosystem structure and species interactions. A growing number of studies suggest that changes to the benthic invertebrate communities, generated by trawling, may increase the availability of food and promote growth and possibly the fisheries yield of target fish species. In this regard, the study aims to assess the effects of trawling disturbance on the diet of the red mullet, Mullus barbatus barbatus, along a gradient of fishing intensity. This mullidae represent one of the main target species of the demersal fisheries in the Western Mediterranean basin, representing one of the most exploited commercial fish species. Stomach contents were analysed to assess the effects of the trawling ban on the diet and to test changes in the diet of the mullidae under different fishing pressure. The study was carried out along the northern coast of Sicily (Southern Tyrrhenian Sea) encompassing two Fishery Exclusion Zones, two gulfs in which the trawling activity has been historically banned: the Gulfs of Castellammare and Patti. Specimens were collected from 50 to 100m depth on muddy bottoms; comparisons between diets along the fishing intensity gradient were made for a size class of red mullet from 11 to 15 cm total length. The spatial distribution of fishing intensity was evaluated through Vessel Monitoring System data analysis, innovative technique that permits to evaluate the fishing activity providing high-resolution fishing effort data. The greater differences in diet composition and diversity were detected between the specimens from trawled and un-trawled area.