First observations of mating behavior of a Mobula cf. birostris (suggesting a melanistic morph) and Mobula mobular in ilha grande bay (Southwestern Atlantic, Brazil): implications for marine conservation and sustainable coastal development

This study presents the first documented observations of mating behavior in Mobula cf. birostris and Mobula mobular in Ilha Grande Bay, located in the Southwestern Atlantic of Rio de Janeiro, Brazil. The individuals were initially identified in previous study as Mobula cf. tarapacana but were subsequently reclassified following expert taxonomic consultation and detailed morphological analysis of drone footage. Among the recorded individuals, one M. cf. birostris exhibited an unusually dark dorsal and ventral coloration, suggesting a possible melanistic phenotype. These findings highlight the reproductive potential and ecological importance of Ilha Grande Bay for large pelagic rays in a region heavily influenced by coastal development. Drone-based monitoring proved to be a powerful non-invasive tool for documenting rare and elusive behaviors, enhancing conservation efforts for threatened marine megafauna. The presence of these species highlights the importance of adopting integrated and sustainable management practices that promote coexistence between marine biodiversity conservation and responsible industrial development in strategic coastal zones. These observations constitute the first evidence of mating behavior in Mobula cf. birostris and M. mobular in the South Atlantic, suggesting that Ilha Grande Bay may function as a reproductive aggregation site for mobulid rays.