The bonytail chub or bonytail, Gila elegans, is a cyprinid freshwater fish native to the Colorado River of Arizona, California, Colorado, Nevada and Utah in the southwestern United States. It was once abundant and widespread in the basin, its numbers and range have declined to the point where it has been listed as endangered (1980), a fate shared by the three other large Colorado basin endemic fish species: Colorado pikeminnow, Humpback chub, and Razorback sucker. It is now the rarest of the endemic big-river fishes of the Colorado River. There are 14 species of the genus, 7 of which are in Arizona.
A bonytail chub can grow to over 2 feet (60Â cm) long. Like many other desert fishes, its coloring tends to be darker above and lighter below, serving as a camouflage. Breeding males have red fin bases. They have a streamlined body and a terminal mouth. Bonytail Chubs have bodies that sometimes arch into a smooth, predorsal hump (in adults). While their skull is quite concave, their caudal peduncle (tailside) is thin, and almost looks like a pencil (hence, âbony tailâ). The coloration of Bonytail Chubs is usually dark dorsally and lighter ventrally, however, in very clear waters, they looks almost black all over. During breeding season, males and females have distinct coloration as well. Mature males have bright red-orange lateral bands between their paired fins; while females have a more subdued coloration that is described with the males.
The bonytail chub was once found in many states, including Arizona, California, Colorado, New Mexico, Utah, and Wyoming. This fish species experienced the most abrupt decline of any of the long-lived fishes native to the main-stems of the Colorado River system and, because no young individuals have been found in recent years, has been called functionally extinct. Bonytail chubs were one of the first fish species to reflect the changes that occurred in the Colorado River basin after the construction of Hoover Dam; the fish was extirpated from the lower basin between 1926 and 1950. They may still be found in the Green River of Utah and perhaps in the larger Colorado River water bodies. Gila elegans was added to the US list of endangered species on April 23, 1980.
There is contention about the reintroduction of the bonytail chub. Some are concerned about the amount of water used to increase stream flows that are required for adequate bonytail chub habitat. Bass fishermen are concerned about facilitating the recovery of the bonytail chub by the removal of smallmouth bass, a popular gamefish. Fears of spreading the quagga mussel, an invasive species that clogs water pipelines and fouls marine equipment, has halted the reintroduction of the bonytail chub in Arizona, pending establishment of a stocking protocol that is satisfactory to Arizona wildlife officials.
Bonytail chub prefer backwaters with rocky or muddy bottoms and flowing pools, although they have been reported in swiftly moving water. They are mostly restricted to rocky canyons today, but were historically abundant in the wide downstream sections of rivers.
Spawning in Lake Mohave has been observed during May, while in the upper Green River, it occurs in the months of June and July. Eggs are laid randomly over the bottom, and no parental care occurs.
Young bonytail chubs typically eat aquatic plants, while adults feed mostly on small fish, algae, plant debris, and terrestrial insects. Little is known about their reproductive habits, but they are thought to spawn in mid-summer and perhaps hybridize with both roundtail and humpback chubs.
The Bonytail chubâs population sizes are small, and continue to become even smaller. The depletion of the population is primarily due to the habitat alterations caused by dams and due to competition and predation by non-native fish.
A USFWS Recovery Plan was established in 1990, and included objectives of protecting the habitats of the Bonytail chub, and even reintroducing hatchery-reared fish into the wild.
The Bonytail Chub Recovery Plan was approved on September 4, 1990, and many refugia for the Bonytail chub exist today in several places: Dexter National Fish Hatchery, New Mexico; Arizona Game and Fish Page Springs Hatchery; Ouray National Wildlife Refuge, Ouray, Utah; Buenos Aires National Wildlife Refuge, Sasabe, Arizona; Niland Native Fish Ponds, California.
- Gila elegans Species Profile, U.S. Fish & Wildlife Service (Accessed 2007 Mar 04)
- USFWS Environmental Conservation Online System page for Bonytail chub
- USFWS Upper Colorado Endangered Fish Recovery Program
- USFWS List of Fish Listed under Endangered Species Act