Ptychocheilus lucius

Examination of allozyme variation among two captive populations and samples from the Green, Yampa, Colorado, and San Juan rivers revealed no significant differences among geographically separated breeding populations (Morizot et al. 2002). However, some populations had rare alleles not shared with other populations. Current barriers to fish movement and widespread stocking of hatchery fish may mask any geographic differentiation that may have formerly existed.

See Carney and Page (1990) for a diagnosis and information on meristic variation. See Mayden et al. (1991) for a morphometric phylogenetic analysis of the genera Mylopharodon and Ptychocheilus (no taxonomic changes were proposed).

Restricted to the Colorado River system, where distribution and abundance are far below historical levels due to the effects of dams and to a lesser degree exotic fishes; populations are now relatively stable.

Historical range included rivers of the Colorado River basin: mainstem Colorado River and major tributaries (Gunnison, White, Yampa, Dolores, San Juan, Uncompahgre, Animas, and Green rivers), from Mexico and Arizona to Wyoming.

Present distribution is drastically reduced. By the mid-1980s, this species occurred only in the Upper Colorado River basin of Colorado, Utah, New Mexico, and Wyoming; mainly in the Green River in Utah and in the Yampa and Colorado rivers in Colorado and portions of Utah; wild fish have not been seen below Glen Canyon Dam since 1968. Adults predominate in the White and Yampa rivers, young in the Green River (Tyus 1986); juveniles reported as rare in the Green River system (see Karp and Tyus 1990).

Spawning occurs in the Green River sub-basin in the lower Yampa River and in Gray Canyon (a segment of the Green River above its confluence with the Price River); nursery areas include the Green River between the Colorado River and the San Rafael River, and a segment of the Green River upstream and downstream from the confluences of the Duchesne and White rivers (Tyus 1991). Spawning also may occur in Labyrinth and Stillwater canyons of the lower Green River, but if so, populations apparently are small (Tyus 1991). River mile 130 on the Colorado River, near the Colorado-Utah state line, has been identified as a spawning site used in multiple years (see Federal Register, 21 March 1994). The presence of small larvae in the upper main-stem Colorado and San Juan rivers indicates successful reproduction, but low numbers suggest limited reproduction or recruitment (Tyus 1991). Colorado pikeminnows recently were recorded in the Little Snake River, Colorado (Wick et al. 1991) and Wyoming (Marsh et al. 1991). The species was reconfirmed as occurring in the San Juan River from 4.4 km downstream from Shiprock, New Mexico, to Lake Powell, Utah (young of year were found near Lake Powell and near the confluence of the San Juan River and Montezuma Creek and near the confluence of the San Juan River and the Mancos River) (Platania et al. 1991). See also Sublette et al. (1990) for relatively recent records from New Mexico and southeastern Utah.

Beginning in the mid-1980s, an experimental population was being established in the Salt and Verde rivers, Arizona (USFWS 1990, Minckley and Deacon 1991).

This species is represented by three wild populations, in the Green River, upper Colorado River, and San Juan River subbasins (USFWS 2011).

Decline resulted probably from a combination of threats, including direct loss of habitat, changes in flow and temperature, and blockage of migration routes by the construction of large reservoirs. In addition, interactions with nonnative fishes may have had a decimating effect in waters not affected by dams (USFWS 2011).

Uncertainty surrounding the effects of climate change to Colorado pikeminnow should be considered for each of the threats as those impacts are realized. For example, the potential for alteration of flows in the basin as a result of climate change should be in the recovery goals. Climate change could have large impacts on the basin's aquatic ecosystem, including (but not limited to): change in the timing of peak flows from an earlier snowmelt; change in the size of peak flows because of altered snowpacks; and higher water temperatures from increased air temperature. Not only would climate change affect the ecology of the species because of the factors listed above, but it also would greatly affect the management of the programs through changes in politics and economics, such as: greater evaporation losses in the larger reservoirs may reduce flexibility of operations; and drier conditions in the basin may cause irrigators to call on their water rights more often or request more water rights. Source: USFWS (2011).