Padrões de estrutura e dinâmica da assembleia de peixes de uma bacia hidrográfica neotropical antropizada, sul do Brasil

Abstract

This Thesis is composed of three chapters that evaluated the patterns of structure and dynamics of fish assemblages of a hydrographic basin neotropical, localized in southern Brazil. The study area includes the Hydrographic Basin Chasqueiro Stream (HBCS), which belong to the hydrographic system of the Mirim Lagoon. The fishes were collected using different fishing artifacts in six sampling points distributed in three biotopes (upstream, reservoir and downstream) along the longitudinal gradient of basin. The first chapter examined the composition of the fish assembly of basin, while the second chapter evaluated the spatiotemporal organization of assemblies using null models of co-occurrence and multivariate analysis using abiotic and biotic data. The third chapter, in turn, investigated the structure and dynamics of the trophic networks of biotopes and the effects of the construction of the reservoir in the basin. A total of 22,853 individuals were collected, distributed in 83 species, 20 families and eight orders. The first chapter revealed a rich fauna of fish for HBCS, with featured for biotopes upstream and downstream, demonstrating greater species diversity in relation to the reservoir. In the second chapter was found that the fish assemblage showed a pattern significantly different of organization spatiotemporal that observed at random, mainly influenced by the structure detected in the biotope upstream and downstream. The third chapter showed a significant difference between the diets of species, interaction density and modularity by three biotopes studied with a larger number of modules on the reservoir and downstream. The reservoir shown to be an ecosystem with more distinct functional characteristics in relation to others two biotopes, revealing the effect of hydrological desconectivity, as well as the presence of invasive species. Furthermore, the larger structural complexity of trophic networks for HBCS was detected downstream, allowing greater interaction intensity in the food web. Along the hydrographic basin impacted by the construction of the reservoir, significant changes occurred in the structure of network, such as reallocation of species to different trophic levels and changes in patterns of nestedness and modularity, with implications for your organization and structural complexity. The information generated in this study may assist in developing management plans and conservation for HBCS, considering the ecosystem variability along of the basin as a predictor model for organizing studies of the structure and dynamic of fish assemblages.