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8 It is unknown whether tertiary bars similar to those used for Colorado squawfish spawning in Yampa Canyon are available in the 15-mile reach of the Colorado River. . There, significant motion of bed material occurs at near bankfull discharge of 22,000 cfs (Van Steeter 1996). These flaws occur on. average once in 4 years. Van Steeter (1996) concludes that flaws of this magnitude are important because they generally remove fine sediment from the gravel matrix which maintains the invertebrate community and cleans spawning substrate. Although the location of spawning areas in the Colorado River .is not well defined, the presence of larvae downstream of the Walker Wildlife Area. in the Loma to Black Rocks reach and near the confluence of the Dolores River. demonstrates that spawning does occur. Osmundson and Kaeding (1989 and 1991) reported that water temperatures in the Colorado River were suitable for spawning in the Grand Junction area. In 1986, a year of high runoff, suitable temperatures for spawning (20' C) occurred in the first week of August. In 1989, a year of low runoff. the mean temperature reached 20' C during the last week of June. Miller et al. (1982) and Archer et al. (1986) demonstrated that Colorado squawfish often migrate considerable distances to spawn in the Green and Yampa Rivers, and similar movement has been noted in the main stem Colorado River. Miller et al. (1982) concluded from collections of larvae and young-of-year below known spawning sites that there is a downstream drift of larval Colorado squawfish following hatching. Extensive studies in the Yampa and upper Gree~ Rivers have demonstrated downstream distribution of young Colorado squawfish from known spawning areas (Archer et a1. 1986: Haynes et al. 1985). Miller et al. (1982) also found that young-of-year Colorado squawfish, from late summer through fall, preferred natural backwater areas of zero velocity and less than 1.5-foot depth over a silt substrate. Juvenile Colorado squawfish habitat preferences are similar to that of young-of-year fish, but they appear to be mobile and more tolerant of lotic conditions away from the sheltered backwater environment. Information on radio-tagged adult Colorado squawfish during fall suggests that fish seek out deepwater areas in the Colorado River (Miller et al. 1982), as do many other riverine species. River pools, runs, and other deep water areas. especially in upstream reaches, are important winter habitats for Colorado squawfish. Very little information is available on the influence of turbidity on the endangered Colorado River fishes. It is assumed, however. that turbidity is important, particularly as it affects the interaction between introduced