Towards an understanding of trawling impacts on Blanes and Palamós submarine canyons. Costa Brava, Spain

Abstract

The continuous over exploitation of marine resources has triggered a progressive expansion of fishing fleets to deeper waters, threatening marine communities and ecosystems. The present study conforms to a detailed analysis of deep bottom trawling surrounding Blanes and Palamós submarine canyons, in the Northwestern Mediterranean Sea. The main idea was to assess the spatiotemporal evolution of the fishing grounds encompassing these canyons, as well as to identify the effects of bottom trawling on the seafloor’s geomorphology and megabenthic assemblages. Vessel Monitoring System (VMS) and Automatic Identification System (AIS) data were used to quantify the pressure exerted by bottom trawling on the study area during the past decade (2008-2019), where as video footage from a Remotely Operated Vehicle (ROV) was used to determine the geomorphological and ecological state of the seafloor, using trawl marks as an indicator of the physical damage of bottom trawling. The results showed that AIS data was an unreliable mechanism to assess fishing effort in bottom trawling grounds surrounding Blanes Canyon. Spatiotemporal evolution of VMS data indicated a growth of fishing areas and fishing effort during the last decade. Furthermore, fishing grounds were highly impacted, with several trawl marks and reduced abundance of megabenthic communities, especially of vulnerable sessile organisms with reduced mobility. In view of the global dimension that this fishing technique encompasses, an integrated management is needed to guarantee a sustainable deep-sea fishery and promote the protection and recovery of deep-sea marine communities