reasons are unclear. Removal of non-native fish near the confluence of the Little Colorado River and Colorado River may have helped the species, but at the same time, drought was lowering the level of Lake Powell and causing water released from Glen Canyon Dam to be much warmer than normal. Typically, water released from the dam is too cold for chub to reproduce. Introduced smallmouth bass have been a predatory threat to humpback chub above the Glen Canyon Dam, but had not been able to get beyond Lake Powell. But as of 2022, smallmouth bass have been found below Glen Canyon Dam, possibly as a result of the low water level at Colorado River and Lake Powell. References Tobin, Mitch. Endangered: Biodiversity on the Brink. Golden, CO: Fulcrum, 2010. William F. Sigler and John W. Sigler, Fishes of Utah (University of Utah Press, 1996), pp. 79–83 USFWS Environmental Conservation Online System page for Humpback chub USFWS Upper Colorado Endangered Fish Recovery Program USFWS List of Fish Listed under Endangered Species Act National Park Service: Grand Canyon National Park − Humpback Chub Translocation Experiment in Shinumo Creek (accessed on 2009-09-01) External links List of Arizona Native Fishes Arizona Desert Museum United States Fish and Wildlife Service Rule Reclassifying the Humpback Chub from Endangered to Threatened (2021) Chubs (fish) Gila (fish) Fish of the Western United States Cyprinid fish of North America Endangered fish Taxa named by Robert Rush Miller Fish described in 1946 ESA endangered species Freshwater fish of North America