Using non-native vegetation to enhance in-stream habitat for native fishes
October 2021 - September 2023
- Bureau of Recalmation
Habitat loss and degradation is one of the leading hypothesized mechanisms for declines in native fish occurrence and abundance in the Colorado River basin. Providing adequate habitat for all life stages of imperiled fishes is a primary management action needed in the San Juan River basin. In-stream habitat in the San Juan River has been simplified by channel narrowing and reduced channel migration due to an altered flow regime and establishment of non-native vegetation. The latter is primarily Russian olive (Elaeagnus angustifolia) that has armored the river banks contributing to habitat simplification to the detriment of native fishes. Low velocity habitats are hypothesized to be important to survival of ESA-listed, young-of-year Colorado Pikeminnow Ptychocheilus lucius and other native fishes. Juvenile Colorado Pikeminnow select for low-velocity habitats in the San Juan River, but these habitats have been reduced due to degradation of in-stream habitat. Given that Colorado Pikeminnow are experiencing continued declines across their range in the Upper Colorado River basin, there is a need to assess further management actions to improve survival and retention. We will use existing non-native woody structure to increase habitat complexity, quantify changes in habitat from the addition of woody structure, and quantify differences in macroinvertebrate densities between reaches with addition of woody structure and control reaches.