Resumen del producto

The regulation of mesh size is important for the effective and sustainable management of fisheries using gillnets,which are the main fishing gear used in artisanal elasmobranch fisheries throughout northwestern Mexico.Gillnet selectivity studies focusing on elasmobranchs have generally evaluated the impact on target species, andinformation on bycatches remains scarce. This study assessed the impact of gillnet selectivity on both targetelasmobranch species and bycatches, by varying the mesh size of gillnets. Sampling was performed from 2009 to2015 in five artisanal fishing grounds located along the northwestern coast of Mexico. The species compositionand ecological parameters of the elasmobranch communities that were caught, as well as the size structure andestimated selectivity models for the main species caught, were compared between four mesh sizes: 10.16, 15.24,20.32 and 25.4 cm (stretched opening). Overall, 32 elasmobranch species were caught, nine of which werecommon to all mesh sizes. Our results indicate that the species composition of the catch varied with mesh size.While the small-sized sharks Mustelus californicus and M. henlei were the main species caught by gillnets with thesmaller mesh sizes, the guitarfish Pseudobatos productus and Zapteryx exasperata, and the Pacific angel sharkSquatina californica were the main species caught gillnets with the largest mesh sizes. Gillnet selectivity wasestimated for these latter four species as well as for the horn shark Heterodontus francisci. Optimum length forthese species varied widely, increasing proportionally to mesh size. These findings emphasize the difficulty ofdetermining an optimal minimum mesh size for multi-species fishery in this area. Finally, recommendations forfuture directions according to the species' vulnerability to fishing are discussed, focusing on the development ofeffective strategies to initiate or strengthen the recovery of elasmobranchs of the northwestern coast of Mexico.

Palabras clave: artisanal fishery; gillnet; Management; northwestern Mexico; selectivity

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