Fish aggregations and reproductive behaviour on mesophotic coral ecosystems of a southwestern Atlantic Oceanic archipelago

Dozens of marine fish species are known to form spawning aggregations, a behaviour that often increases the species vulnerability to fisheries. Therefore, it is widely recommended for aggregation sites to be considered a conservation priority, and implementation of management measures on those sites is essential. Here, we report for the first time the reproductive behaviour of the marbled grouper Dermatolepis inermis, observed at a lower mesophotic coral ecosystem of Fernando de Noronha, an oceanic tropical archipelago in the southwestern Atlantic. The event was characterised by an aggregation of six adult fish, displaying courtship behaviour and reproductive colouration. We also recorded an aggregation of about 20 dog snappers Lutjanus jocu at the same site, but no reproductive behaviour was observed. Finally, another aggregation was observed in the island's upper mesophotic reefs, with 25 terminal phase individuals of the Brazilian endemic parrotfish Sparisoma amplum. Our report reinforces the biological importance of mesophotic coral ecosystems, and highlights the urgent need of governmental policies for studying, monitoring, and protecting those reefs.