Diversity and distribution of cryptobenthic fishes and their association with epibenthic fauna in a subtropical estuary

Cryptobenthic fishes (CF) are cryptic species that exhibit mimicry with their benthic environment and can be either detritivorous or zoobenthivorous. Few studies have examined the influence of epibenthic macrofauna on CF diversity. This study analyzed the colonization and spatiotemporal succession of CF and macrofauna in fish-specific autonomous reef monitoring structures (FARMS) at Paranaguá Estuarine Complex (Brazil). Five FARMS were installed in localities in São Miguel, Amparo and Nova Brasília, which represented an estuarine gradient. Sampling was conducted every 2 months from October 2023 to August 2024; 303 individuals belonging to seven species associated with the FARMS were recorded, five of which were classified as CF. Bathygobius soporator was the dominant species in all of the sampled areas. To identify the epibenthic macrofauna, scrapings were performed every 2 months over the 10-month experiment from the FARMS installed in Nova Brasília and São Miguel. A dominance pattern of crustaceans, annelids and gastropods species was observed in Nova Brasília. In São Miguel, the macrofauna was dominated by annelids, bivalves, crustaceans, and ascidians. Individual FARMS were used as sampling replicates to evaluate spatial and temporal variation in fish assemblages. Fish community structure differed among areas, with a significant area × sampling event interaction indicating area-specific temporal trajectories, whereas no common temporal effect was detected. Macrofaunal assemblages differed between Nova Brasília and São Miguel, but no significant overall effect of fouling time was detected. Fish and macrofaunal community configurations were significantly concordant (procrustean randomization test, r = 0.636, P = 0.0348). These results indicate that cryptobenthic fish assemblages are spatially structured and that their temporal variation is associated with local changes in fouling communities, although the observational design did not demonstrate direct causal effects of macrofauna on fishes.