Evidence of trawl disturbance on mega-epibenthic communities in the Southern Tyrrhenian Sea

Bottom trawling has direct impacts on benthic communities. These impacts are modified by the environmental context in which they occur. Communities that occur in habitats subjected to low levels of natural disturbance are considered to be the most vulnerable to bottom trawling. The present study examined the impact of otter trawl fisheries on epifaunal assemblages of the Southern Tyrrhenian Sea (Central Mediterranean Sea), across the continental shelf and down to the meso-bathyal plain. Using a long time-series of non-target epifaunal species collected by experimental otter trawl surveys, differences in assemblage structure and composition were detected among areas that experienced different levels of fishing intensity relative to Fishery Exclusion Zones. Areas that experienced the highest levels of trawling had a significantly lower abundance of crinoids and ophiuroids; the former are important structuring fauna. The epifauna assemblage composition in the areas that had been subjected to the heaviest levels of fishing activity were characterised by a greater number of scavenging species that are resilient to the effects of fishing. Although the heavily trawled areas had higher diversity than the less heavily fished areas, this was associated with the absence of K-selected species such as crinoids and dominance by r-selected scavenging biota.