Drivers of abundance and biomass of Brazilian parrotfishes

Parrotfishes may affect the structure of benthic communities and reef ecosystem functioning. Despite extensive studies worldwide, parrotfishes in the southwestern Atlantic are relatively understudied, limiting our ability to propose effective management strategies. We assessed abundance, biomass and size class distribution of parrotfish assemblages in northeastern Brazil and identified habitat preferences based on reef attributes. Outer-shelf reefs sustained larger individuals and higher biomasses for all species (except Sparisoma radians). In contrast, inner-shelf reefs supported higher abundances of small individuals. Even though most species occurred across all areas, their abundances, biomass and size-class distributions were variable and related to their respective feeding modes and reef attributes. Benthic cover, reef structural complexity, depth and distance from the coast affected the composition of parrotfish assemblages, but had different effects on each species. The endemic greenbeak parrotfish Scarus trispinosus was more abundant on calcareous substrates and higher-complexity reefs. Sc. zelindae and Sp. amplum were more common in deeper biogenic reefs further from the coast, which were characterized by high abundances of sponges, stony corals and cyanobacterial mats. Sp. axillare and Sp. radians were more abundant on reefs that had high cover of large-bladed macroalgae, while Sp. frondosum was ubiquitous across all studied reefs. Such heterogeneity in habitat use is suggestive of functional complementarity rather than functional redundancy among parrotfish assemblages. Conservation of Brazilian endemic parrotfishes requires protecting reefs with diverse attributes and a better understanding of habitat connectivity and the role of different habitats in parrotfish reproduction and life cycle.