The effects of local and regional environmental factors on the structure of fish assemblages in the Pirapó Basin, Southern Brazil

Abstract

This study aimed to observe patterns in the structure of fish assemblages in streams with different levels of urbanisation, as well as, relationships of these patterns with local and regional environmental factors. We predicted that regional environmental factors would account for more assemblage variation than local regional environmental factors. Data from 10 streams in a gradient of urbanisation in Maringá County, Brazil, were used to characterize fish assemblages’ and environmental factors. Discriminant function analysis was used to test differences between streams and environmental factors. Associations between the structure of fish assemblages and environmental factors in local and regional scales were observed with direct gradient analysis (CCA and pCCA) and relative's contribution quantified by inertia partition techniques. Indicator values were used to find characteristic species in streams with different impacts levels. The environmental factors and structure of fish assemblages were different in streams with different urbanisation levels in regional and local scales. In agreement with the hypothesis tested, the environmental factors as land use, hydrology, geomorphology, chemical and physical habitat characteristics pointed out strong association with structure of fish assemblages in streams with different urbanisation levels. So, the results reveal that the structure of fish assemblages is influenced by environmental factors in different spatial scales in impacted environments, suggesting that efficient management actions should be improved if environmental factors are considered in local and regional scales.