Fish communities in seasonally isolated lagoons of the Upper Paraná River basin, Southeastern Brazil

Marginal lagoons are natural nurseries of commercially important fish species and preferential habitats for sedentary and small-sized fish species. The composition and abundance of fish communities in seasonally isolated lagoons of the Turvo River, qualitative and quantitative changes in the dry and rainy seasons, as well as their relationship with environmental factors, were investigated. The material was sampled in both seasons in six marginal lagoons. Ichthyofauna was studied through species richness, diversity, evenness, qualitative and quantitative similarities, and ecological associations between samples and species. A total of 7457 specimens, distributed among 52 species, 40 genera, 19 families, and five orders, were recorded. The most abundant species were Astyanax lacustris, Serrapinnus heterodon, Pterygoplichthys ambrosettii, Hyphessobrycon eques, and Moenkhausia intermedia. Fish communities showed remarkable seasonality with the highest values of species richness and abundance in the rainy season. In both seasons, higher species richness was found in environments with the largest area and amount of macrophyte species. Canonical correspondence analysis revealed that water temperature and alkalinity were significantly associated with ichthyofauna structure. Despite adverse conditions in isolated seasonal lagoons, global fish diversity was high due to heterogeneous environmental conditions. These habitats must be considered priority areas for fish conservation and management.