From bycatch to litter: a systematic map of the ecological impacts of fishing in European seas

Ecological impacts from fishing are multifaceted, ranging from bycatch of sensitive species to physical seabed disturbance and cascading effects on food webs and biodiversity. A systematic review approach was applied to map the wealth of literature available on ecological fishing impacts in European seas. Over 2000 papers were screened, resulting in 527 papers that underwent full assessment and from which a systematic map database was created. Results show that impacts from demersal trawls on fish and benthic invertebrates were most studied, with catch or bycatch of organisms and physical disturbance of the seabed as key pressures. Pressures like discarding and fisheries-related litter were much less studied, as were impacts on marine mammals, sharks, rays, seabirds, food webs, reptiles, cephalopods, plants and plankton. Most papers studied impacts on the abundance or mortality of organisms, followed by community composition and biodiversity. Half of the papers were from the Mediterranean Sea, with fewer from other areas. We further illustrate the utility of the database with two case studies: one rich in papers, focusing on ecological impacts from bycatch of endangered, threatened or protected species, and one less well represented, focusing on ecological impacts from fisheries-related litter. For each case study, regional differences and key relationships between pressures, gear types and ecosystem components were identified, including information on scale, resolution and sampling methodology, followed by future research directions. Our systematic mapping approach enables users to reproduce and expand the database for future studies, summarising the knowledge needed to implement ecosystem-based fisheries management in Europe.