Monitoramento de elasmobrânquios com a utilização de técnicas não invasivas e não letais (Baited Remote Underwater Video – BRUV) em Fernando de Noronha, ilha no Nordeste brasileiro

Abstract

Fish fauna assessments with traditional capture methods are undesirable in marine reserves. In the aquatic environment, the visual census is biased due to fish-diver interactions, such as shyness or avoidance behavior of large target species. This study presents the monitoring of elasmobranchs in the Fernando de Noronha Archipelago, in northeastern Brazil, sampled with an independent non-destructive remote underwater video (BRUVS) system. Five species of elasmobranchs were identified, belonging to three orders and four families. There was a predominance of the order of Carcharhiniformes with more than half of the identified species (52.35%). Three species of sharks and two of rays were identified. Two distinct types of habitats could be observed with the video analyses, and the species were distributed according to their characteristics. Among the shark variants, Carcharhinus perezii (n=37) was identified in reef areas, as it inhabits coral reefs. However, the lemon shark (Negaprion brevirostris), mostly (n=29), was detected in sandy environments, it has a demersal and pelagic habit in shallow tropical and subtropical coastal waters around coral reefs. While the Ginglymostoma cirratum, it holds the natural habitat in the rocky reefs and sand plains. Furthermore, with regard to rays, the highest number of stone rays was observed in the sand environment, as Hypanus berthalutzae inhabits sand plains and coral reefs. The only individual spotted ray was detected in a rocky environment, an ecosystem in which Aetobatus narinari is frequently associated. The permanent BRUVS records that were obtained through this research can be examined repeatedly to verify the original findings, used for comparisons with new data or to gather additional information. Thus, information on species richness and relative abundance within the island provided a baseline for future monitoring efforts in order to assess the impact of long-term environmental changes.