Padrão de distribuição das assembleias de peixes juvenis em um estuário do semiárido do Brasil

Abstract

Estuaries are dynamic coastal ecosystems in which the interaction between the hydrological regime and the mixing of fresh and oceanic waters creates a gradient of variables that reflect on the structure of the fish community, as well as their spatio- temporal pattern. These characteristics are used as filters, that is, determining factors that select species ecologically similar, hence producing different groups of species along an environmental gradient. These filters can act on hierarchical scales, partitioning the diversity of species within the components α (local diversity), β (variation of diversity between sites) and γ (regional diversity). Therefore, the aim of this study was to analyze the composition, structure, hierarchical partitioning and if beta diversity is determined either by turnover or nestedness of fish assemblages in the Mamanguape river estuary, influenced by hydrological changes (rainy and dry periods). The composition and structure of the estuarine fish assemblages were characterized by a few dominant species in numerical abundance and biomass, being these considered core species. In addition, abundance and diversity increased with the proximity to the ocean due to adequate salinity conditions and greater habitat availability in these areas. The catch of fish in the estuary was higher during the rainy season, related to the recruitment period of many species that coincide with the environmental changes. The Canonical Correspondence Analysis indicated salinity and chlorophyll-a as the main filters of the spatial distribution of fish assemblages, separating them along the three zones according to the osmoregulation capacity of each species and the availability of resources in the zones. In the analysis of the hierarchical partition of the fish assemblages, the dissimilarity of the species composition was higher in the upper level (β3), influenced mainly by the turnover in both hydrological periods, suggesting the importance of the environmental heterogeneity for the fish diversity in this estuary.