Fish assemblages in an environmentally complex narrow coastal region in the Southwestern Atlantic Ocean: an alternative nursery habitat for fishery species

Abstract

The narrow coastal waters south of the Río de la Plata estuary are an oceanographically dynamic area where small-scale or artisanal fisheries occur. We analyzed 95 fishing bottom trawls from research surveys, along with oceanographic data collected during 2016 and 2017. Multivariate analyses (PERMANOVA, SIMPER, CAP) were applied todetermine the spatial distribution of fish density, diversity and assemblage structure, as well as their relationship with the oceanographic environment. We estimated the length- frequency distribution of Sciaenid species to determine the presence of juveniles in the area. We recorded forty-three coastal fish species (15 commercial and 28 noncommercial) with the families Sciaenidae and Rajidae accounting for approximately ~80% of the catches. Marine migrants were the most dominant in terms of species, followed by marine stragglers and estuarine residents. We detect differences in assemblages between surveys, primarily associated with nine species. Bottom salinity and temperature had a significant influence on the spatial structuring of discriminant species and functional groups. Sciaenid juveniles were found in areas with low salinities and shallow habitats, while adults were distributed in deeper and saltier waters. This work highlights the importance of physical conditions on fish assemblage dynamics in a complex environment, as well as the significant role of a narrow coastal band (~5 km) as a nursery habitat for commercially important fish species.