Effects of natural hydrological variability on fish assemblages in small Mediterranean streams: Implications for ecological assessment

► Assemblages show high resilience to hydrological variability in least disturbed sites. ► Hydrological variability can act jointly with anthropogenic disturbances. ► Hydrological variability may influence the ecological assessment in disturbed sites. ► Ecological assessment tools should consider temporal and environmental variability. ► Seven fish metrics were selected as the most appropriate to include in a biotic index.