This paper relates life cycle characteristics of fishes, their environmental tolerances, habitat requirements, and resilience against hydromorphological disturbances to a recently developed river typology providing a hierarchy of spatial units. It aims to identify the most relevant spatiotemporal scales for river restoration and environmental assessment.
Most fish species, except diadromous and some potamodromous species can complete their life cycle within a river reach and form sustainable populations within a river segment. Considering the home range of most species, representative sampling at the reach scale will cover all functional river elements, hydraulic, and geomorphic units, while accounting for their temporary or sporadic use by fish. Therefore, the reach scale appears as practicable and sufficient scale for fish-based assessments and as highly relevant planning unit in hydromorphological river restoration practice. Nonetheless reach-scale characteristics are largely inherited from large scale geomorphic processes and multiple pressures at the catchment scale that may impact aquatic communities and river restoration success at the lower spatial scales.