Abstract
Studies on fish assemblages in streams point out, that understanding the relationship between species and their environment is crucial for conservation. The present study aimed at evaluating the effects of changes in abiotic variables on the composition and structure of fish assemblages in Neotropical urban streams from southern Brazil with different levels of urbanization. The composition and structure of fish assemblages showed significant differences along the urbanization gradient observed in the streams. Tolerant and non-native species were found in more urbanized sites. A matrix correlation revealed a relationship between abiotic variables and the spatial pattern of structure and composition of fish assemblages. Abiotic variables, such as total phosphorus, dissolved oxygen, and conductivity, determined the distribution of fish assemblages. Streams without urban influence exhibited intrinsically low species richness, suggesting that they are highly susceptible to species loss and diversity reduction. Thus, changes in water quality or hydrological conditions induced by urbanization may intensify these impacts.
Highlights
Understanding spatial and temporal changes in population size and distribution, as well as mechanisms and processes responsible for these changes, is an important goal of community studies (Ornellas & Coutinho, 1998)
Fish assemblage A total of 4,768 individuals were caught, which were ascribed to 25 species of 6 orders and 10 families (Table 2)
Regarding the urbanization gradient, the highest number of species was captured in the Jacutinga Stream (20 species; 1,709 individuals), followed by Pinheirinho (19 species; 1700 individuals) and Panambi streams (18 species; 1359 individuals; Table 2)
Summary
Understanding spatial and temporal changes in population size and distribution, as well as mechanisms and processes responsible for these changes, is an important goal of community studies (Ornellas & Coutinho, 1998). Biotic and abiotic factors affect the distribution and abundance of fish, in both pristine and impacted streams (Schlosser, 1991; Paul & Meyer, 2001). Effects of abiotic variables on the distribution of fish assemblages construction and deforestation has increased surface runoff due to soil sealing (Paul & Meyer, 2001). These factors may increase sediment load and discharge, altering channel geometry (Montgomery & Buffington, 1998). Our main objective was to understand how changes in abiotic variables affect the composition and structure of fish assemblages in streams with different anthropogenic activities
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