By Stephen Petersburg

On 13 July 2000, one of the West’s rarest fish species was returned to the Green and Yampa Rivers. Five thousand hatchery-reared juveniles of the endangered bonytail (Gila elegans) were released in the lower Yampa near Echo Park in Dinosaur National Monument, and another 5,000 were released in lower portions of Browns Park in the Browns Park National Wildlife Refuge and in the national monument. These releases will be augmented by additional future releases in an attempt to reestablish wild populations of bonytails.

One of four endangered large-river fishes in the Colorado River system, the bonytail had been virtually extirpated from wild riverine habitats. The other three endangered species are the Colorado pikeminnow (Ptychocheilus lucius), razorback sucker (Xyrauchen texanus), and humpback chub (G. cypha). The State of Utah listed the bonytail as protected in 1974, while Colorado listed it as endangered in 1976. In 1980 the bonytail was federally listed as endangered under the Endangered Species Act of 1973.

The bonytail is a member of the minnow family Cyprinidae. It has a streamlined body that narrows markedly toward the tail. Its back is gray or olive, its sides are silvery, and its belly is white. Its large fins are also characteristic of the species. Bonytails may reach lengths of greater than 24 inches (61 centimeters) and may live nearly 50 years. They are closely related to other chub species in the Colorado River system, and intergrades with the humpback chub and the roundtail chub (G. robusta) have frustrated geneticists for many years.

Dams in major river channels, such as the Flaming Gorge and Glen Canyon Dams, are the proximate cause of the decline of endangered Colorado River fishes. Dams alter many characteristics of riverine habitats, and the new habitats favor nonnative fish species, many of which compete with or prey on the endangered species. The bonytail was once common from the lower reaches of the Colorado River to well upstream of Dinosaur National Monument. One of the last riverine areas that wild bonytails occupied into the late 1960s was around Echo Park. Remnant populations have persisted in reservoirs in the lower Colorado River basin and in hatcheries.

Stocking the rivers with bonytail is a cooperative undertaking by the U.S. Fish and Wildlife Service, National Park Service, Colorado Division of Wildlife, and Utah Division of Wildlife Resources. The bonytails were raised in the Wahweap Fish Hatchery of the Utah Division of Wildlife Resources near Page, Arizona. The Colorado Division of Wildlife and the U.S. Fish and Wildlife Service transported the fishes to the release sites, where the National Park Service assisted with the releases. The agencies are members of the Upper Colorado Recovery Implementation Program, which consists of federal and state agencies, environmental groups, and water- and power-user organizations in Colorado, Utah, and Wyoming. The goal of the program is the recovery of endangered fish species while allowing development of water resources for human uses.