Alpha and beta diversity patterns of the reef fishes’ early life stages and conservation implications in the Abrolhos Bank, Brazil

Abstract

Coral reefs and associated habitats, such as mangroves, seagrass beds, and rhodolith beds, provide vital ecosystem services but are among the most threatened marine areas. This has led to a decline in the abundance of many reef-associated organisms, particularly coral reef fish. Understanding the dynamics of settlement and recruitment in reef fishes and their relationship with habitat is therefore essential for their conservation. Achieving ecosystem and species conservation objectives requires prioritizing areas with greater species richness and diversity, alongside those with higher densities of species threatened by exploitation at local and regional scales. In this study, we analyzed the alpha and beta diversity patterns of postlarval and juvenile coral reef fish in the Abrolhos Bank. Using light traps and underwater visual censuses (UVCs), we assessed diversity indices and decomposed beta diversity into turnover and nestedness components to explore spatial dynamics and habitat relationships. Our findings provide pioneering insights into the alpha and beta diversity patterns of postlarval and juvenile coral reef fishes in the Abrolhos Bank, revealing spatial variation in fish assemblages across sites. Beta diversity was predominantly driven by the turnover component, indicating significant species replacement between locations. Rhodolith beds and coastal reefs, such as Cassurubá and Paredes Parcel, were identified as critical habitats for maintaining fish stocks. We recommend prioritizing these areas in conservation strategies and promoting connectivity between them, considering the importance of larval input and recruitment for reef fish populations in the Abrolhos Bank.