ABSTRACT Catchment-modelling techniques, although not yet widely used in biological contexts, may be a valuable tool in the management and conservation of stream fishes. This study was undertaken to evaluate the potential of a catchment-scale hydrologic model, the Soil and Water Assessment Tool (SWAT), to explain characteristics of stream fish assemblages and to enhance current field-based stream assessments., Stream fish assemblages, instream habitat, geomorphology, and water quality were surveyed in 16 study catchments in Ohio, USA. Subsequently, SWAT was used to model stream discharge, sediment flux and concentration, and nitrogen and phosphorus yields for each catchment., Principal component analysis (PCA) and multiple linear regression [...]