The endangered bonytail Gila elegans, a large-bodied, main-stem cyprinid endemic to the Colorado River Basin of the American Southwest, was once widespread and abundant in warm-water-stream reaches. Negative effects of altered flow and temperature regimes downstream of dams, other habitat changes, and establishment of nonnative fishes have reduced populations of native fish throughout the basin, and wild bonytails may be extirpated. Hatchery reared bonytails are stocked in formerly occupied habitat to rebuild depleted populations, but their ecology is poorly understood. In 2002?2007, sampling in the middle Green River from upstream and downstream of stocking locations in Dinosaur National Monument documented survival of bonytails for [...]