|Scientific Name:||Gila elegans|
|Species Authority:||Baird & Girard, 1853|
|Red List Category & Criteria:||Critically Endangered B1ab(v)+2ab(v); C2a(i) ver 3.1|
|Reviewer(s):||Smith, K. & Darwall, W.R.T.|
|Facilitator/Compiler(s):||Hammerson, G.A. & Ormes, M.|
This species is listed as Critically Endangered because no self-sustaining populations are known to exist; hence extent of occurrence and area of occupancy by viable populations are essentially nil, and number of locations is zero if only self-sustaining populations are counted; trend is unknown, but wild population is probably declining; adult population size is unknown but very small.
|Range Description:||Bonytails were formerly abundant throughout the Colorado River and its larger tributaries, including the Green River north to the reach now inundated by Flaming Gorge Reservoir in Wyoming and Utah, the Yampa and Gunnison rivers in Colorado, and the Colorado River in Arizona, Colorado, Nevada, and California), and probably also the San Juan River in New Mexico and the Gila and Salt rivers in Arizona (Lee et al. 1980, USFWS 1990, Muth et al. 2000). Documented records exist for Lake Havasu, Lake Mohave, and Grand Canyon in the Lower Colorado River Basin; and Lake Powell, the Colorado River (Cataract Canyon, Green River confluence, Utah; Black Rocks, Colorado), Gunnison River near Delta, Colorado, Green River (Gray Canyon, Utah; Dinosaur National Monument, Colorado and Utah; Hideout Canyon, Utah), and lower Yampa River, Dinosaur National Monument, Colorado), in the Upper Colorado River Basin (USFWS 2002).
An unknown but small number of wild adults exist in Lake Mohave on the mainstem Colorado River of the Lower Colorado River Basin (i.e., downstream of Glen Canyon Dam, Arizona), and there are small numbers of wild individuals in the Green River and upper Colorado River subbasins of the Upper Colorado River Basin (USFWS 2002). USFWS (2002) listed only two locations (Lake Mohave on the Arizona-Nevada border and Lake Havasu along the Arizona-California border) where wild bonytails have been documented since 1990.
As of the early 1990s, populations were being established in urban lakes in Tempe, on the Buenos Aires NWR, and at TNC's Hassayampa Reserve, all in Arizona; plans called for stocking of experimental populations into Arizona streams (Minckley and Deacon 1991).
|Range Map:||Click here to open the map viewer and explore range.|
Currently no self-sustaining populations of Bonytail exist in the wild (USFWS 2002).
Total adult population size is unknown but apparently is very small.
This species formerly was widespread and abundant; today it occurs in the wild as only a few scattered individuals and is regarded as functionally extinct (USFWS 1990, Muth et al. 2000). In the Green River basin, this species has been virtually nonexistent in recent collections (Muth et al. 2000). The last observed large concentration of Bonytail occurred 1954 when about 500 adults were observed spawning over a gravel shelf in Lake Mohave, Arizona-Nevada (Jonez and Sumner 1954). Collections of Bonytail in Lake Mohave yielded at least 50 specimens in the 1970s and 1980s, but USFWS (2002) reported that only one Bonytail subsequently was captured there. Significant numbers of Bonytail were last captured in the Upper Colorado River Basin (lower Yampa River and Green River below the Yampa) in the 1960s and early 1970s, shortly after the closure of Flaming Gorge Dam. Since then, only a few single captures were recorded (all in the 1980s) in the entire Upper Colorado River Basin (USFWS 2002).
Recent trend is unknown because so few Bonytails have been captured. Wild population probably is declining.
|Habitat and Ecology:||
Gila elegans is a warm-water species that appears to favour main-stem rivers regardless of turbidity, usually in or near deep swift water, in flowing pools and eddies just outside the main current. It also has been found in reservoirs. Available data suggest that habitats required for conservation include river channels and flooded, ponded, or inundated riverine habitats, especially those where competition from non-native fishes is absent or reduced (USFWS, Federal Register, 21 March 1994).
Spawning occurs probably in spring over rocky substrates; spawning in reservoirs has been observed over rocky shoals and shorelines (USFWS 2002). Flooded bottomland habitats appear to be important growth and conditioning areas, particularly as nursery habitats for young (USFWS 2002).
|Major Threat(s):||Threats to the species include habitat modifications resulting from streamflow regulation, dams that function as movement barriers on main-stem rivers, competition with and predation by nonnative fish species, hybridization (possibly), and pesticides and pollutants (USFWS 2002). The significance of, and factors leading to, hybridization with other Gila species are unclear, and this factor is not regarded as an important threat at the present time (USFWS 2002). However, hybridization should be evaluated as Bonytails are released into the wild and populations become established (USFWS 2002). Low population size and lack of recruitment are major obstacles to recovery.|
Management actions needed include the following (USFWS (2002):
|Citation:||NatureServe 2013. Gila elegans. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 30 August 2015.|
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