Why implement measures to conserve the diversity of Elasmobranchs? The case of the northern coast of Brazil

The biodiversity and commercial exploitation of sharks and rays Sharks and rays are members of the subclass Elasmobranchii Bonaparte, 1838, and are found in the tropical, subtropical, temperate and cold waters of all entire world’s seas and oceans, inhabiting both offshore and coastal areas in pelagic, demersal, reef and estuarine environments, and even in freshwater habitats (Compagno, 1984). However, data on the biology of the elasmobranchs are scant for some regions, such as the Southwestern Atlantic, where the populations of even critically endangered species are still captured by commercial fisheries, as well as being sold in local fish markets (Tavares et al., 2013; Palmeira et al., 2013). The verification lists of the diversity of species of the class Chondrichthyes (Huxley, 1880), which includes the Elasmobranchii, vary considerably around the world, and are based on the available data, which often leads to misinterpretations and inconsistencies in the listings of valid species (Last and Séret, 2016; Last et al., 2016a; Last et al., 2016b). Given these considerations, a scientific review of the group was conducted, based on recent data on the taxonomic diversity, geographic distribution, and the depth of the waters inhabited by these species. By November 7th 2015, a total of 1139 species of elasmobranch had been catalogued (Figure 1A), representing 15 orders, 58 families, and 193 genera. This new listing includes nine orders, 34 families, 105 genera and 509 species of shark, and six orders, 24 families, 88 genera and 630 species of ray. The species that are currently being described were not considered valid for this inventory (Weigmann, 2016). Recently, data on the diversity of the marine chondrichthians that occur in Brazil has been updated (Rosa and Gadig, 2014) (Figure 1B), and concluded that the subclass Elasmobranchii is represented by 11 orders, 33 families, 75 genera and 159 species, six orders, 22 families, 43 genera, and 89 species represented by Sharks, while the rays are classified in five orders, 11 families, 32 genera, and 70 species. Overall, 49 of these 159 elasmobranch species are included in one of the three principal threatened categories of the IUCN, i.e., Critically Endangered, Endangered and Vulnerable (Figure 2A: Supplementary Table 1). The Brazilian Environment Ministry (IBAMA ordinance number 445 of December 17, 2014) classifies 53 of these species in one of the threatened categories. In addition to this large number of threatened species, there are a relatively large number of species (50 according to the IUCN Why implement measures to conserve the diversity of Elasmobranchs? The case of the northern coast of Brazil Conservation of Elasmobranchs off the northern coast of Brazil