|Listed||April 23, 1980|
|Description||Large, silver chub with greenish back.|
|Habitat||Turbid, swift-flowing rivers.|
|Food||Insects and algae.|
|Reproduction||Spawns in the spring.|
|Threats||Dam construction, water diversion, competition with non-native fishes.|
|Range||Arizona, California, Colorado, Nevada, Utah|
The bonytail chub, Gila elegans, is a relatively large chub, averaging 12 in (30 cm) in length. Its chunky body is silver with a greenish tinge along the back. The head is flattened, the back slightly humped, the eyes very small and of little use. The narrow tail terminates in a V-shaped caudal fin. The breeding male's belly turns bright orange-red. The bonytail chub was once considered a subspecies of the roundtail chub (G. robusta ) but has since been accorded full species status.
The bonytail chub is omnivorous, feeding mainly on terrestrial insects, larvae, algae, and detritus. In spring it spawns in schools over rocky shoals of smaller tributaries.
This species is found in larger rivers and displays a high tolerance for turbidity. It is most frequently associated with eddies just outside the main river current. The bonytail chub is susceptible to changes in water temperature and flow, and low levels of chemical pollution.
The bonytail chub was once abundant throughout the Colorado River and its larger tributaries. It has been collected from the Green River in Wyoming and Utah, Yampa and Gunnison Rivers in Colorado, the Colorado River in Arizona, Nevada and California, and the Gila and Salt Rivers in Arizona.
In the 1960s a dramatic decline in bonytails was recorded in the Green River after the Flaming Gorge Dam was completed. The Bureau of Reclamation has since adjusted water flows from the dam to improve downstream habitat, but no corresponding recovery of the bonytail has been noted. Recent surveys indicate that the bonytail chub may survive only in Lake Mohave along the Arizona-Nevada border. The surviving wild population appears to consist of older fish that are not reproducing.
Massive reservoir impoundment and hydroelectric dams have changed the character of the Colorado River basin. Many stretches of river—for example, the Dolores River below the McPhee Dam—are dry through portions of the year. Massive amounts of water are diverted each year for irrigation and human consumption. The U. S. Fish and Wildlife Service (FWS) has determined that any additional diversion of water from the Colorado River would jeopardize the survival of the bonytail chub, humpback chub (G. cypha ), and the Colorado squawfish (Ptychocheilus lucius ).
Introduction of exotic fishes into the river basin has also contributed to the bonytail chub's decline. Predation on larval chubs by red and redside shiners may account for the absence of bonytail fry. Non-native fishes now outnumber native fishes in the Colorado River basin.
In 1984 the FWS convened the Upper Colorado River Basin Coordinating Committee to defuse controversy over the federal listing of several Endangered fishes. The committee, a forum for discussion and negotiation, consisted of representatives of the FWS, the Bureau of Reclamation, the states of Colorado, Utah, and Wyoming, and private water development interests. In 1988 the committee forged an unprecedented regional agreement to improve water flow and quality in the Colorado River basin.
Conservation and Recovery
In 1986, the FWS and the Division of Refuge Management initiated a cooperative effort to hold Endangered Colorado River fish in refuges along the lower Colorado River. Use of these refuges— typically riverside ponds with controlled river access—permits fish fry to be reared to subadult size before being released into the river, improving survival chances. The bonytail chub was the first fish to be transplanted to a pond at Imperial National Wildlife Refuge in Arizona, using stock from the Dexter National Fish Hatchery.
Bonytail fry have also been stocked in ponds at the Havasu, Cibola, and Buenos Aires national wildlife refuges and subsequently returned to the river with promising results, but the bonytail chub is still a long way from recovery. The Colorado River Fishes Recovery Team recommended in 1987 that all bonytails netted in the wild be transported to the Dexter facility for use in the captive propagation effort.
The 1994 revised Recovery Plan for the species noted that the recovery goal, in the short-term, is to prevent extinction, and in the long-term, to address quantitative goals for downlisting and eventual delisting. Recovery criteria will be developed after the completion of various actions, including the prevention of extinction by establishing a genetically diverse captive population for reintroduction into the wild. The revised plan also calls for the gathering of essential information about the life history and habitat requirements of the fish; the resolution of taxonomic problems in Colorado River basin chubs (the bonytail as well as the humpback and roundtail); and the development of quantitative recovery goals and a long-term habitat protection strategy.
On March 21, 1994 the FWS published the final rule designating Critical Habitat for the bonytail chub in portions of the Upper Basin of the Colorado, Green, and Yampa Rivers; and in the Colorado River in the Lower Basin.
Regional Office of Endangered Species
U.S. Fish and Wildlife Service
Eastside Federal Complex
911 N.E. 11th Ave.
Portland, Oregon 97232
Regional Office of Endangered Species
U.S. Fish and Wildlife Service
P. O. Box 25486
Denver Federal Center
Denver, Colorado 80225
Ono, R. D., J. D. Williams, and A. Wagner. 1983.Vanishing Fishes of North America. Stonewall Press, Washington, D.C.
Sigler, W. F., and R. R. Miller. 1963. Fishes of Utah. Utah State Department of Fish and Game, Salt Lake City.
U.S. Fish and Wildlife Service. 1990. "Bonytail Chub Revised Recovery Plan." U.S. Fish and Wildlife Service, Denver.
"Bonytail Chub." Beacham's Guide to the Endangered Species of North America. . Encyclopedia.com. (January 16, 2019). https://www.encyclopedia.com/environment/science-magazines/bonytail-chub
"Bonytail Chub." Beacham's Guide to the Endangered Species of North America. . Retrieved January 16, 2019 from Encyclopedia.com: https://www.encyclopedia.com/environment/science-magazines/bonytail-chub
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