An overview of bottom trawl selectivity in the Mediterranean Sea

In the Mediterranean Sea, where bottom trawling for demersal species is the most important fishery in terms of landings,around 75% of the assessed fish stocks are overfished. Its status as one of the world's most heavily exploited seas and the onesubject to the highest trawling pressure has become a global concern. An extensive overview of bottom trawl selectivity studieswas performed to assess the sustainability of this fishery in the Mediterranean. The selectivity parameters were collected from93 peer-reviewed publications from 10 countries, totalling 742 records and 65 species. Our review highlighted that i) the catch ofthe bottom trawls commonly employed in the Mediterranean, although they comply with current codend mesh regulations, stillincludes immature individuals of 64-68% of the species investigated, and individuals under the minimum conservation referencesize (MCRS) of 78% of the species investigated, and that ii) the MCRS set for 59% of the species analysed is well below theirlength at first maturity and is therefore ecologically inadequate. Although square-mesh codends are slightly more selective, themodels developed herein demonstrate that improving size and species selectivity would require considerably larger meshes, whichmay significantly reduce profitability. The urgent need to mitigate the biological impacts of bottom trawling in the Mediterraneanshould be addressed by promoting the adoption of more ecologically sustainable fishing gears through the introduction of moreselective meshes or of gear modifications.