Hierarquia ambiental e a ictiofauna de riachos de cabeceira da bacia do rio Sorocaba (SP-Brasil)

Abstract

The effects of environmental factors related to different scales on the taxonomic and functional organization of stream fish communities were evaluated. This study was divided into two chapters whose data were obtained by sampling fish fauna in 19 70 - meters lenght sites in 11 streams, located in the Sorocaba river Basin, upper Paraná river system, northeastern São Paulo State, Brazil. In CHAPTER I we hypothesized and tested a hierarchical organization model where riparian landcover would influence bank composition and light availability, which in turn would influence local environmental characteristics and control fish assemblages. In CHAPTER II we aimed to identify which factors (i.e., regional: sub-basins structure; local environmental filters: meso and microhbitats) were the most important on the organization of stream fish composition. We used electrofishing to collect specimens and environmental assessment was based on descriptors of riparian zone landcover and in-stream habitats of the sampling sites. Multivariate analyzes indicated that riparian zone landcover can be considered a higher level causal factor in a network of relations, controlling other environmental factors and, ultimately, functional composition. In addition, in-stream factors may act as environmental filters with coupled with regional processes, control fish assemblages distribution patterns. Our results highlight the importance of hierarchical and scale-based approaches to ecological studies and restoration strategies.