Release efficiency and selectivity of four different square mesh panel configurations in the Basque mixed bottom trawl fishery

Square mesh panels (SMPs) have been proposed as a bycatch reduction measure that can increase the escape of non-target fish species without significantly changing the economic value of the catch. However, previous studies have found that SMPs do not significantly increase non-target fish escapes because there is a low probability of fish making contact with the panel.This study aimed to determine whether i) adding white LED lights at different positions of the SMP, ii) changing the size of the SMP, and iii) changing the position of the SMP in the trawl improved the release efficiency of a square mesh panel (SMP) installed at the top panel of the extension piece of the trawl. The study focused on reducing catch of undersized hake (Merluccius merluccius), a main target species for the Basque multispecies trawl fishery in the Bay of Biscay, and blue whiting (Micromesistius poutassou), which is considered a “choke” species in the fishery (one with a low quota). The position of LED lights did not significantly affect the SMP’s release efficiency for any species. However, increasing panel size increased escapes of blue whiting, and placing the SMP in the lower net panel increased escapes of hake. These species-specific results highlight the challenge of simultaneously improving the selective properties of gear for species with different behavior, especially in mixed demersal fisheries.