Geomorphology variables predict fish assemblages for forested and endorheic rivers

This dataset contains data from field collections described in the paper: "Shields, R., Pyron, M., Arsenault, E., Thorp, J., Minder, M., Artz, C., Costello, J., Otgonganbat, A., Mendsaikhan, B., Maasri., A. (2022) Geomorphology variables predict fish assemblages for forested and endorheic rivers. Ecology and Evolution. ECE-2021-08-01367". Stream fishes are restricted to specific environments with appropriate habitats for feeding and reproduction. Interactions between streams and surrounding landscapes influence the availability and type of fish habitat, nutrient concentrations, suspended solids, and substrate composition. Valley width and gradient are geomorphological variables that influence the frequency and intensity that a stream interacts with the surrounding landscape. For example, in constrained valleys, canyon walls are steeply-sloped and valleys are narrow, limiting the movement of water into riparian zones. Wide valleys have long, flat floodplains that are inundated with high discharge. We tested for differences in fish assemblages with geomorphology variation among streams in US and Mongolia montane forested and endorheic ecoregions. Montane rivers of Mongolia are pristine and have few invasive species, compared to montane rivers of the western US. Sites where we collected were defined as geomorphologically unique river segments (i.e., functional process zones; FPZs) using an automated ArcGIS-based tool. This tool extracts geomorphic variables at the valley and catchment scales and uses them to cluster stream segments based on their similarity. We collected a representative fish sample from replicates of FPZs. Then, we used constrained ordinations to determine if river geomorphology could predict fish assemblage variation. Our constrained ordination approach using geomorphology to predict fish assemblages resulted in significance using fish taxonomy and traits in several watersheds. The watersheds where constrained ordinations were not successful were next analyzed with unconstrained ordinations to examine patterns among fish taxonomy and traits with geomorphology variables. US and Mongolia montane river fish assemblages varied with geomorphology variables including river elevation, gradient, valley width, channel sinuosity, valley slope, and annual precipitation. These results provide evidence that fish assemblages respond similarly and strongly to geomorphic variables on two continents. We recommend increased conservation of river ecosystems of the US and Mongolia, to prevent further degradation.