Abstract
Abstract: Aim Our study was carried out to develop a multimetric index suitable for urban wadeable streams in Sorocaba, a large-sized city from the Atlantic rainforest in south-eastern Brazil. Methods Twenty-seven stream stretches were selected for environmental and fish evaluation. Twenty ecological metrics were tested over an environmental gradient between the reference and degraded stretches. Candidate metrics were screened for range, responsiveness, and redundancy. We calculated a multimetric fish index (MFI) subdivided into five quality classes: reference ≥ 0.8, 0.6 ≤ good < 0.8, 0.4 ≤ moderate < 0.6, 0.2 ≤ poor < 0.4, and bad < 0.2. Results Four metrics were adequate for discriminating higher biotic quality from degraded stretches. Five stream stretches (18%) were classified as a reference or good, and 16 (60%) were poor or bad. Three reference stretches could be used for a hydromorphological restoration programme. Conclusion Our results indicated that biological integrity was altered, which was indicative of severe environmental degradation. Our study results may be useful for a management and restoration project of the Sorocaba/Médio Tietê hydrographic basin.
Highlights
Stressors can be considered as any physical, chemical or biological parameters or entities that directly or indirectly result in biotic responses of concern (USEPA, 2017)
Twenty ecological metrics were tested over an environmental gradient between the reference and degraded stretches
Candidate metrics were screened for range, responsiveness, and redundancy
Summary
Stressors can be considered as any physical, chemical or biological parameters or entities that directly or indirectly result in biotic responses of concern (USEPA, 2017). Urbanization can cause perturbations to a system through sewage effluent, channelization, and riparian vegetation reduction These multiple stressors can make it difficult to determine individual stressor relative importance (Paul & Meyer, 2001; Walsh et al, 2005). The loss of breeding, feeding, and resting habitat can modify the fish community. These mechanistic pathways are not well studied in urban streams (Wenger et al, 2009). The fish assemblage similarity of urban with reference streams, species richness and diversity, proportions of lithophilic spawners fish, and sensitive species decreased with increasing urbanization (Helms et al, 2005; Wang et al, 2001; Morgan & Cushman, 2005). Historical species pool and stream characteristics can shape fish communities, with urbanization playing a rather individual role (Czeglédi et al, 2020)
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