Comparison of Habitat Composition and Cutthroat Trout Abundance at Two Flows in Small Mountain Streams

Abstract

Abstract We assessed habitat features measured in the recently developed basinwide habitat inventory for their relations to abundance of native cutthroat trout Oncorhynchus clarki in small streams of the Rocky Mountains. We also evaluated the manner in which habitat and fish abundance changed as streamflow declined during the summer sampling season. Our observations corroborated the assumption that the basinwide habitat inventory is a valid technique for identifying channel unit types with differing levels of use by cutthroat trout. We found higher biomass of cutthroat trout in pools than in glides or riffles. Plunge pools had higher biomass than dammed pools. Biomass was greater in low-gradient riffles than in rapids, and no fish were found in cascades. We observed an increase in the abundance of channel unit types, changes in the physical dimensions of channel unit types, and a decrease in overall stream length with declines in flow. We concluded that the basinwide habitat inventory does identify habita...