Warm Water Invasive Fish Management at the -12 Mile Slough

Glen Canyon National Recreation Area is initiating a Environmental Assessment (EA) to analyze proposed Colorado River slough channelization project at River Mile -12 within the park.  River Mile -12 is located on the Colorado River three miles below the Glen Canyon Dam and 12 miles upriver from Lees Ferry, AZ. This EA will consider channelizing the slough to help prevent successful reproduction of high-risk, warm water, non-native fish, particularly smallmouth bass and green sunfish.

The presence of non-native fish in Glen Canyon, Marble Canyon, and Grand Canyon threatens the populations of native and federally listed fish species, including the humpback chub and razorback sucker, and the rainbow trout sport fishery. Non-native fish are passing through the Glen Canyon Dam due to lower Lake Powell surface elevations. Lower lake levels in 2022 and 2023 resulted in higher dam outflow temperatures, leading to smallmouth bass and green sunfish reproduction below the dam. Reducing reproduction in the River Mile -12 Slough could help reduce the likelihood of downstream expansion and establishment in Glen Canyon, Marble Canyon, and Grand Canyon.

The EA is being prepared in compliance with the National Environmental Policy Act (NEPA) to provide a decision-making framework that effectively evaluates potential issues and impacts to the area's resources and values.

Contact Information

Buddy Fazio, Chief of Science and Resource Management
928-608-6265