Assessing Habitat Requirements of Young Colorado River Cutthroat Trout by Use of Macrohabitat and Microhabitat Analyses

We used both microhabitat and macrohabitat analyses to better assess habitat requirements of young Colorado River cutthroat trout Oncorhynchus clarki pleuriticus. Microhabitat analyses revealed that among a range of stream types, young cutthroat trout consistently preferred slow water (<0.06 m/s) and depths over 3 cm. Suitable habitat of this type was provided by different types of pool habitat within the geomorphically diverse study streams. Macrohabitat analysis indicated that the density of young cutthroat trout was positively correlated with the abundance of spawning gravel and negatively correlated with stream depth (adjusted R2 = 0.67). This relationship helped explain the absence of young cutthroat trout from some stream reaches that had suitable microhabitat but that often lacked suitable spawning habitat. The two types of habitat analysis provided complementary information concerning the habitat requirements of young Colorado River cutthroat trout in the study streams.