Performance of sorting grids on catching elasmobranchs in a multispecies Mediterranean bottom trawl fishery

Elasmobranchs are among the most threatened long-lived marine species in the Mediterranean Sea. Incidental catch and intense fishing effort are considered the major threats to their conservation. To date, no Mediterranean countries has adopted specific technical measures within current conservation plans to mitigate potential impacts on vulnerable elasmobranchs. This study aimed to evaluate the effectiveness of new elasmobranch bycatch reducing devices (BRD) in a Mediterranean multispecies bottom trawl fishery (northern central Adriatic Sea, one of the most exploited basins in the Mediterranean). Specifically, two types of grids were tested: a novel shark excluder device (SED) and a flexible grid (Flexgrid). Effectiveness was evaluated in terms of bycatch and commercial catch reduction, relying on the different sizes of elasmobranchs and the main commercial species. Results showed that preliminary tests with SED were effective in excluding elasmobranch species. Catches made with this grid showed no significant difference for targeted crustacean (mantis shrimp, Squilla mantis), however, commercial losses were shown for some large bony fish. Flexgrid did not affect the catches of the main target species, such as the red mullet (Mullus barbatus), European hake (Merluccius merluccius) and mantis shrimp, but also retained small-spotted catshark (Scyliorhinus canicula). The effectiveness of the grids apparently was affected by the small size of the elasmobranchs captured. The study showed that SED and Flexgrid are valuable solutions for elasmobranchs if combined with other conservation measures (e.g. seasonal fishing closure in critical areas and good practices). Finally, strong cooperation between fishers, scientists, and managers is critical to identify the best management options in a regulatory framework where only a few elasmobranch species are formally protected. Interestingly, the study also yielded the identification of two potential aggregation-nursery areas for the small-spotted catshark (Scyliorhinus canicula) and the common smooth-hound (Mustelus mustelus).