Measuring the spatial and seasonal variability of community structure and diversity of fish by-catch from tropical shrimp trawling in the Colombian Caribbean Sea

The highest rates of incidental catch of non-target species is associated with shrimp bottom trawl fisheries. This could lead to adverse effects on the structure and functioning of ecosystems. However, the structural and functional variability of fish communities captured as by-catch from this fishery in the Colombian Caribbean Sea have been poorly documented. We examined commercial fishing hauls in two areas (Gulf of Morrosquillo and adjacent coralline islands) during the rainy and dry seasons. The biomass and numeric abundance of fish species were estimated using by-catch data collected using the swept area method, and the demersal fish community structure was characterized using ecological, taxonomic and functional diversity indices. During the two seasons, 161 taxa were recorded, and 92 of them were present throughout the whole area. Ecological indices showed significant differences among areas and seasons, with lower values in the Islands area and during the wet season. However, the taxonomic diversity and functional indices do not show clear differences but instead indicate that the Islands area was the zone with a lower taxonomic and functional variation, which indicates lower ecological redundancy in comparison to the Gulf.