The habitat use of ariid catfishes in coral reefs in northeastern Brazil

Ariidae species occur across a wide range of habitats from freshwater to fully marine environments and are typically associated with soft-bottom substrates. However, they are sometimes associated with hard-bottom substrates such as coral reefs, but such association is poorly documented. This study describes the occurrence and habitat use of six ariid species in the coral reef of Penha Beach, northeastern Brazil. We deployed gill nets monthly alongside the coral reef over a year between 2023 and 2024, and we sampled 256 individuals representing six ariid species. Bagre filamentosus, a marine catfish, was the most abundant species throughout the year. Species composition varied seasonally, and an RDA analysis showed that variation in species abundances was associated with precipitation and air temperature, with Cathorops spixii occurring primarily during the wet season. B. filamentosus and Sciades proops showed male-biased sex ratios across all seasons (exact binomial tests), and males of B. filamentosus exhibited higher mass gain per unit length during the dry season (t-test). Diet composition varied among months and according to the species' habitat affinity, although effect sizes were small and seasonal differences were weak. These findings suggest that ariid catfishes use coral reef systems as opportunistic foraging and refuge habitats, with habitat use probably linked to their life cycle and the connections between coral reefs and estuaries.