Brook trout
Colorado River cutthroat trout were once abundant in mountainous tributaries of the Green and Colorado rivers, but non-native brown, brook, and rainbow trout had displaced them by the 1930s. They still survived in some isolated pockets, however, and these populations have been used to restore the cutthroats to many areas in their historic range. One of the largest strongholds was, and is, Trappers Lake in Colorado's Flat Top Mountains. However, in 1984, brook trout invaded because a flood washed them downstream from nearby Crescent Lake. By 2003, brook trout comprised 40 percent of the lake's fish population. Brook trout have an advantage over cutthroat trout because they spawn in fall. By the time Colorado River cutthroats hatch in August, brook trout fingerlings may be able to eat them. Colorado Parks and Wildlife is controlling their population with large nets and selective removal.