Distância da costa, profundidade, zoantídeos e algas frondosas moldam a estrutura da assembleia de peixes recifais em recifes rochosos da Baía da Ilha Grande, RJ

Abstract

The abundance and spatial distribution of reef fishes can be influenced by local habitat characteristics like benthic composition, topographic complexity and depth, and both the natural and anthropogenic gradients associated with coastal proximity. Additionally, larger areas of rocky substrate may increase the species-area relationship for these organisms. This study aimed to investigate the variation in reef fish assemblages on islands of different sizes along a gradient of distance from the coast, identifying the key predictors influencing their distribution in the Ilha Grande Bay (BIG), Rio de Janeiro, Brazil. Six sites in the central region of BIG were sampled, including three on small islands (perimeter < 2.3 km) and three on Ilha Grande (perimeter > 100 km). Multivariate analyses were used to assess variation in assemblage structure, species richness, and trophic groups according to island size (taking into account the variability among sites) and to identify the predictors that best explained assemblage variation. Island size was not associated with changes in any of these parameters, possibly due to the short distance between islands and a reduced isolation effect. However, macroalgal and zoanthid cover, depth, and distance from anthropogenic disturbance sources were the primary predictors of variability in assemblage structure, abundance, and trophic groups among sites. These findings suggest that in small spatial scales, local environmental characteristics play more significant role in the spatial dynamics of these communities.