Marine protected areas are not representative of chondrichthyan species assemblages in the Southwest Atlantic

Evaluating the representativeness of species assemblages and species richness in a network of protected areas is key to reach a balanced and equitable network design. However, representativeness has not been assessed for sharks, rays and chimaeras (chondrichthyans), one of the most threatened vertebrate classes. Here, we evaluate the representativeness of chondrichthyan biodiversity in the current network of closed fishing areas (CFAs), and marine protected areas (MPAs), and on a proposed network of relevant conservation areas (RCAs) in the Southwest Atlantic, a large, globally significant region for chondrichthyan conservation. For each Southwest Atlantic bioregion, we estimated the geographic distribution of species richness, and related CFA, MPA and RCA coverage with species richness, using generalized linear and generalized additive models. Within each bioregion, large expanses of high species richness were, in general, not covered by CFAs, and one bioregion had no CFA coverage whatsoever. Three out of the six bioregions had null MPA coverage. Local areas of high species richness had negligible MPA coverage. RCA coverage of local high-richness areas was much higher than either MPA or CFA coverage. This represented a marked improvement; however, vast areas of high bioregional species richness had no coverage, and one bioregion lacked any RCA coverage. Current CFAs and MPAs do not provide adequate protection for the chondrichthyan biodiversity of the Southwest Atlantic, and must be improved to reach full representativeness. Global conservation agendas promoting big MPAs in remote seas should be integrated to regional networks to avoid unbalancing and halting future MPA networks.