Role of the habitat condition in shaping of epifaunal macroinvertebrate bycatch associated with small-scale shrimp fisheries on the Southern Brazilian Coast

Abstract

Shrimp captures have reached a record in Southern Brazil, and some populations show signs of overexploitation. One shrimp species in particular, Xyphopenaeus kroyeri, abundant in Brazilian landings, is caught by bottom trawl. Trawl fishery is recognized by the impacts it causes on the seabed and on organisms that live in or on the substrate. The present study was conducted in traditional fishing areas on the southern Brazilian coast to assess the conditions of the habitat and the ecological aspects of the marine macroinvertebrate community at 3 areas (Barra do Sul, Penha and Porto Belo) in the Central and Northern Coast of the state of Santa Catarina (southern Brazil). Bottom water and sediment data were used to analyze the differences between the sites. Macroinvertebrate captures were used to analyze ecological aspects of the communities such as composition, diversity and patterns associated with the abiotic variables and habitat conditions. We used a trawling vessel for samplings. The results showed a homogeneous water mass between the areas. However, the sediment characteristic differentiates the areas and contributes to the species composition’s heterogeneity between the samples. The ABC and species-ranking curves results suggest moderate disturbances in the three areas, but with a better structure for the Porto Belo communities. In this context, Barra do Sul was characterized by an environment relatively poor in sediment structure, the abundance and biomass of species. In contrast, Porto Belo and Penha were the opposite. Since trawling changes the sediment’s characteristics are strongly correlated with the diversity and the permanence of sensitive species, we suggest that increased small-scale trawling activities might contribute to the substrate’s homogenization and reduce species diversity in these areas. Therefore, constant surveys to monitor the physical structure and the community and its dynamics in trawling areas are indispensable for the conservation of species and fisheries’ sustainability.