Effects of water temperature, turbidity, and rainbow trout on humpback chub population dynamics

H chub (Gila cypha Miller 1946), found only in the Colorado River Basin, was one of the first species to be given full protection under the Endangered Species Act of 1973. Habitat alterations, such as changes in flow and water temperature caused by dams, and the introduction of nonnative fish have contributed to population declines in humpback chub and other native fish. These habitat alterations provide ideal conditions for the nonnative sport fish, rainbow trout (Oncorhynchus mykiss Walbaum 1792). Managers have long sought to balance recovery of humpback chub with a viable rainbow trout fishery. However, finding this balance requires understanding how environmental conditions and rainbow trout have affected humpback chub populations. Recent findings indicate that the Colorado River can be managed for rainbow trout while maintaining a healthy humpback chub population in Grand Canyon National Park.