Assessing patterns of ichthyofauna discarded by an artisanal shrimp fishery through selectivity experiments in a coastal lagoon

We evaluated spatio-temporal effects of fishing gear selectivity on the ichthyofauna discarded by the artisanal shrimp fishery in Celestun Lagoon (Mexico). Selectivity experiments, based on the covered codend method, were carried out in different zones (seaward, middle, inner) and climatic seasons (Nortes, Dry, Rainy) using two bottom nets with different mesh size codends: 13 mm (MS13: currently used in the fishery) and 25 mm (MS25). The number of fish species retained with MS13 was higher than with MS25, and the abundance, biomass and proportion retained of fish discards were significantly higher with MS13 for all seasons and zones. Additionally, community indices (species richness, diversity and evenness) calculated for the ichthyofauna retained by the MS13 codend were significantly the highest. The length of 50% retention was at least 2 times larger with MS25 than with MS13 for the 5 most abundant fish species in the catches. We conclude that an increase in mesh size would reduce substantially the impact on the ichthyofauna discarded by the artisanal shrimp fishery in this coastal lagoon.