The effectiveness of marine protected areas on the spatio-temporal patterns of reef fish in the Southwest Atlantic.

This study explored spatio-temporal patterns influencing reef fish richness and abundance in two coastal islands within marine protected areas (MPAs) in southeastern Brazil. Data were collected using a remotely operated vehicle (ROV) during the 2022 seasonal cycle, with samples taken day and night. A total of 16 661 individuals from 81 species was recorded. The results showed that fish abundance was higher during the day, in winter and in areas with high temperatures. At night, in autumn, behavioural changes were observed in schooling species. Seasonal variations, including temperature changes and the oceanographic characteristics of the study area, influenced fish abundance and species composition, favouring tropical and subtropical species. Depth affected the islands differently: higher abundance was observed in deeper waters at Anchieta Island State Park, while shallower waters at Mar Virado Island showed greater abundance due to habitat complexity. Diurnal variation in richness was significant at Mar Virado Island, probably due to increased nocturnal predation. For fishing-targeted species, the islands showed significant effects on species composition and abundance, highlighting the importance of protected areas. The study offers key insights into reef fish dynamics, emphasizing the role of spatio-temporal variables in shaping communities and supporting conservation strategies in MPAs.