Impacts on biodiversity from codend and fisher selection in bottom trawl fishing

Fisheries have important impacts on marine biodiversity. In this work, combined information the abundance, species richness, diversity indices, composition, trophic level and vulnerability index were examined for first-time to detect differences in five units related trawl fishing: fish assemblage entering codend, escaping, retained, discarded landed fractions, derived by gear fisher selection practices. The work was based a case study conducted Mediterranean Sea, using three different meshes codend (40mm-40D 50mm-50D diamond meshes, 40 mm-40S square meshes) cover of codends with small mesh size. general, fishing produces an escaping fraction that always lower index, similar indices level, composition compared codend. almost all cases, fishers selected as landings lowest highest level. contrast, Although did not differ significantly escapees terms 40S showed higher percentage number individuals, less composition; addition, abundance discards retained catch (0.6:1) than other two (0.9:1). It suggested urgent modification elimination highly vulnerable (e.g. Elasmobranchs) is needed, species-selectivity should be improved allowing escape or avoiding minimize biodiversity losses.