Species richness and reproductive modes of chondrichthyans in relation to temperature and fishing effort in the Southwestern Atlantic Shelf (34–54° S)

Abstract

The aim of this study was to characterize the spatial distribution of species richness and reproductive modes of chondrichthyans in relation to temperature, and the overlap with areas closed to bottom trawling and areas of high fishing effort. Generalized additive models were used to assess the relationship of species richness and number of reproductive modes to environmental variables. High chondrichthyan richness was associated with high thermal variability and was observed between 34° and 41° S from a depth of 80 to 200m. Of the high richness areas, 14.9% overlapped with the closed areas established in 2012, and there was no overlapping with high fishing effort zones. Areas with a high number of reproductive modes were observed between 33° and 42° S at depths of less than 80m and higher sea surface temperature values. Of the areas with a high number of reproductive modes, 23.63% overlapped with the areas closed to trawling, whereas 32.47% overlapped with zones of high fishing effort. South of 34° S, during the spring and summer months, ∼26% of the shelf is closed to trawl fishery. However, the relocation of fishing effort was associated with areas with high chondrichthyans species richness and a high number of reproductive modes. The areas closed to trawling are a valuable management tool for chondrichthyans when they are monitored to assess geographical and seasonal delimitation, as well as the problems associated with the relocation of fishing effort.