Relationship of Fish Mesohabitat to Flow in a Sand-Bed Southwestern River

Abstract We quantified the availability and utilization of habitat types by eight small-bodied cyprinid fish species, including the federally threatened Pecos bluntnose shiner Notropis simus pecosensis, in the Pecos River, New Mexico. The Pecos River is a medium-sized, sand-bed river with a highly variable hydrograph and some reaches characterized by historic and recent periods of flow intermittency. Fish habitat was described in four reaches at flows of 0.05–2.29 m3/s by means of a simultaneous, coordinated program of channel topographic surveys, mesohabitat mapping, fish sampling, and measurement of microhabitat and chemical parameters. We determined that fish habitat in this sand-bed river was effectively described at the mesohabitat scale. Furthermore, mesohabitats were visually distinguishable and separable by means of hydraulic and geomorphic parameters and the relationship between flow and depth, velocity, and velocity : depth ratios. The eight cyprinid species in the Pecos River primarily used fou...