Native Fish of the Grand Canyon

Abstract: Native fish in the Grand Canyon evolved in a habitat that was extremely physically variable but biologically isolated from other river systems. The assemblage of fish species native to the Grand Canyon is highly endemic to the Colorado River basin: most of the species are found in no other river systems. With the construction of dams and other water infrastructure projects and the introduction of numerous nonnative fish species, the environment these fish now inhabit has switched to being more physically constant and biologically crowded. These changes have caused three of the eight fish species native to the Grand Canyon to be extirpated from the canyon stretch and left only one of the native species at population levels high enough to be considered common in Grand Canyon National Park. Four of the eight are listed as endangered and are now monitored and managed in attempts to recover their populations.