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• Movement Humpback chub have previously been documented to move less than roundtail chub and other Colorado River fishes (Valdez and Clemmer 1982, Archer et al. 1985, Kaeding et al. 1990, Valdez and Ryel 1995, Chart and Lentsch 2000). Archer et al. (1985) found in Black Rocks that roundtail chub moved more than humpback chub. Valdez and Ryel (1995) later supported that finding by ~ stating that humpback chub moved substantially less than other Colorado River fishes. Valdez and Clemmer (1982) recaptured seven humpback chub in Desolation/Grayeanyons that had originally been captured in the same locations. Chart and Lentsch (2000) further supported this finding by reporting the recapture of nine chub at the original capture locations in Desolation/Grayeanyons. ~ In Westwater Canyon, little movement of humpback chub and roundtail chub has been documented in the past, but the limited data indicates humpback chub move more than roundtail chub (Chart and Lentsch 1999). A substantially larger dataset of recaptured humpback chub and roundtail chub from this study indicates similar levels of movement: 20% of humpback chub were recaptured in a different location; 11 % of roundtail chub were recaptured in a different location. However, from . 1998 to 2000, there was a substantially higher rate of movement by humpback chub among all three sites. All roundtail chub movements from 1998 to 2000 were between Cougar Bar and one of the other two sites, while, in addition, Chart and Lentsch (1999) observed limited movement from Miners Cabin to Hades Bar. As long-term recaptures increased in 1999 and 2000 with a smaller period of time between capture ~ occasions for an individual, there was less evidence of movement in recaptured individuals. Tn 1998, the number of recaptured individuals from 1997 was relatively low. Long-term recaptures were more representative of humpback chub that had been captured from 1992 to 1996, and these individuals exhibited more movement among sites within Westwater Canyon. Thus, short-term site fidelity is supported by the data. However, once humpback chub move to a new location, short-term ~ site fidelity maybe re-established for that area. A radiotelemetry component added to future population estimates may provide insight to within and among site movements of humpback chub in Westwater Canyon. Movement of humpback chub and roundtail chub between Black Rocks and Westwater Canyon has ~ been previously documented (Chart and Lentsch 1999; McAda 2003). The capture of three humpback chub and three roundtail chub from 1998 to 2000 in Westwater Canyon that were originally tagged in Black Rocks supports the theory of continued exchange between these two areas. Furthermore, McAda (2003) documented 14 humpback chub that had originally been tagged in Westwater Canyon prior to 1998 that were recaptured in Black Rocks from 1998 to 2000. This . migration of approximately 10.5 miles between Black Rocks and Westwater Canyon violates the assumption of closure associated with the models being used for population estimates. The frequency of movement between the two canyon areas is similar to that between areas within Westwater Canyon and exceeds the one migrant per generation required to prevent genetic differentiation (Mills and Allendorf 1996). It maybe.more appropriate to consider Black Rocks/Westwater Canyon humpback chub a single population and analyze it as such. ~ 11