Responses of the ichthyofauna to urbanization in two urban areas in Southeast Brazil: Fid-Bau Portal

Responses of the ichthyofauna to urbanization in two urban areas in Southeast Brazil

Peressin, Alexandre / Cetra, Mauricio

Abstract In this study, we evaluated the trophic structure and composition of the ichthyofauna in streams from non-urbanized and urbanized areas in two municipalities with approximately 30,000 inhabitants. We sampled fish fauna in nine pool-run stretches, four located in urban and five in non-urban areas. We adapted a physical habitat index (PHI) that summarized the physical attributes of the habitat, and a fish-based biotic integrity index (IBI) for the trophic structure of fish assemblage. Higher median scores of habitat parameters characterized non-urban stretches owing to better riparian vegetation and shading, bank stability and larger substrates. Diversity, richness and evenness indexes, as well as the abundance and biomass comparison (ABC), did not differ between urban and non-urban areas. The PHI was significantly correlated with the IBI and a non-metric multidimensional scaling (NMDS) analysis showed differences in the composition of the ichthyofauna. These results illustrated a common process in fish assemblages subjected to environmental impact, in which the generalist species replaced more specialist species, altering the species composition but maintaining a similar community structure. In general, the species responses were dependent on their trophic plasticity and foraging habitats. We showed that in a gradient of habitat alteration, species composition and thophic structure are better indicators of degradation than simple diversity indexes. We also discuss the implications of the urbanization in small towns toward changes in the species composition of freshwater fish, and the utilization of biotic and abiotic characteristics to document these changes.