Source data from the National Aquatic Resource Survey's National Rivers and Streams Assessment containing benthic macroinvertebrate and fish taxa data and environmental predictor variables for stream sites. Results data contains estimated of taxa richness for invertebrates and fish for both ecoregions and hydrologic units. This dataset is associated with the following publication: Hughes, R.M., A. Herlihy, R. Comeleo, D. Peck, R. Mitchell, and S. Paulsen. Patterns in and predictors of stream and river macroinvertebrate genera and fish species richness across the conterminous USA. Knowledge and Management of Aquatic Ecosystems. EDP Sciences, LES ULIS, FRANCE, 424: 2023014, (2023).