Demersal chondrichthyan assemblages in the western Mediterranean Sea

The situation for chondrichthyans in the Mediterranean Sea is particularly concerning, with 53% of the assessed species classified as threatened (IUCN). Chondrichthyans constitute an important percentage of the catch for multi-specific fisheries, particularly for bottom trawling, but a minor part of landings. Monitoring programs are essential to assess the status of chondrichthyan communities. Our research provides updated information on the structure and status of the demersal chondrichthyan assemblage inhabiting trawling fishing grounds from the northern Spanish Mediterranean (GFCM GSA06). Data was obtained from 187 hauls conducted by commercial bottom trawlers on a seasonal basis between June 2020 and January 2022 as part of the projects ECEME and SAP-ICATMAR. Surveys ranged from 50 to 800 m deep. A total of 17 chondrichthyan species belonging to 12 families occurred throughout the area, shaping two different assemblages in relation to depth. Richness increased with depth and decreased with latitude, but the most common species all along the area were Scyliorhinus canicula, Galeus melastomus, Etmopterus spinax and Torpedo marmorata, accounting for the largest proportion of total density and biomass. We mapped the geographical, bathymetrical, and seasonal distribution patterns in relation to sex and maturity stage for the most common species. Thus, we shed light into their sexual and ontogenetic segregation patterns and unravel important aspects of their ecology. The aim of this work was to improve the required knowledge to assess the status and susceptibility of the chondrichthyan populations inhabiting the western Mediterranean Sea, aiding to a more efficient management of the associated fisheries