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hatching dates (see above), sampling occurred closest to the spawn in 1996, but even that trip was several weeks subsequent to the calculated spawning peak. The observed sex ratio (M:F) of chubs in Westwater Canyon was fairly balanced overall: 58:42 and 46:54 for humpback and roundtail chubs, respectively. However, sexing cyprinids innon-breeding condition presented the researchers with some difficulty. Examination of the recapture history indicates that the gender constancy (not necessarily correctness) from capture to capture for humpback chub was 77.4% and 75% for roundtail chub. Amore thorough examination of the field records would likely clear up some of the confusion, i.e., defer to the later determination when the fish was older and the fish's sex more discernable. Movement Two humpback chubs tagged by the Colorado Division of Wildlife in Black Rocks at RM 136.1 _ were recaptured two days later in Westwater Canyon. One roundtail tagged in our study at RK 194.4 in 1993 was recaptured the following year by Colorado Division of Wildlife crews, 23.4 km upstream at RK 217.8 in Black Rocks. This was the only recorded exchange of chubs between these purported populations during the course of this study. It is our feeling that these two large adult humpback (296 mm and 372 mm TL; the larger of which was the largest humpback recaptured in the current study) were displaced by handling stress rather than exhibiting directed movement. The UDWR has observed similar (although shorter) movements on a short term basis (1-2 day durations) within Westwater Canyon as have other researchers (Archer et al. 1985). The majority, 82.8%, of humpback recaptures revealed no net movement. The humpbacks that did relocate appear to have done so randomly. Fish tagged at the middle sampling site, Cougar Bar, offer the best test for movement (Figure 17). Thirty-one percent of the humpback chubs initially captured at Cougar Bar were recaptured either 2.4 km downstream (at Hades Bar) or 4.8 km upstream (at Miner's Cabin). The greatest exchange was between the two closest sampling sites: Cougar Bar (RK 194.4) and Hades Bar (RK 192). None of the humpback chubs tagged at Miner's Cabin were recaptured at either of the downstream locations and only 5.8% of the recaptured humpbacks tagged at Hades made the short trip upstream to Cougar Bar. Roundtail chubs displayed an even greater fidelity to their original capture location (Figure 18). Ninety-two percent of the roundtail recaptures indicated no net movement. Humpback chubs persist (greater survival or remain in the capture area) longer in Westwater Canyon than do roundtail chub (Figures 19 and 20). The capture probability of humpback chubs tagged in 1992, 1993 and 1994 remained approximately constant or increased slightly for the first three years following the tagging event. With the exception of fish tagged in 1993, the capture probability for marked roundtail chubs declined precipitously after the first year. Growth Incremental growth (growth /days elapsed between captures) is presented for both species in Figure 21. Many individuals of both species displayed negative growth; either real shrinking or error in field measuring. Both explanations stem from the fact that native chubs grow slowly once they reach 200 mm TL. An analysis of the incremental growth against length at capture yielded negatively sloped regression lines crossing the zero growth threshold near 300 mm TL for both species. Growth of three size classes of late juvenile and adult sized chubs is presented in Table 16. 18