The purpose of this project is to determine if a newly formed rapid on the Colorado River is acting as a barrier to invasive non-native fish moving upstream from Lake Mead into the Grand Canyon National Park (GCNP). These non-native fish would threaten native desert fishes upstream to include the endangered Razorback Sucker and the Humpback Chub. The project will fill knowledge gaps on fish movement, species composition, and population dynamics in this minimally studied section of the Colorado River, and inform managers on whether active management actions (e.g. native fish translocations; non-native removals) may be required to conserve native fishes in the western Grand Canyon.