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The observed sex ratio (IvI:~ of chubs in Westwater Canyon was fairly balanced overall: 58:42 and 46:54 for humpback and roundtail chubs, respectively. However, sexing cyprinids in non- breeding condition presented the researchers with some diffiailty. 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 detenrunation 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. This is 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 r 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). One roundtail chub (~F~D3o~FaD) moved 4.1 miles upstream from Hades Bar to M'iner's Cabin over the course of almost three years. Two other fish (a humpback chub (7F7DOF6E65) and a roundtail chub (ISFBS11223)), moved 2.6 miles upstream from Cougar Bar to Miner's Cabin and one humpback (lF41~SOC4Fj moved upstream from Hades Bar to Cougar Bar. Several other humpbacks and roundtails traveled the short distance downstream from Cougar Bar to Hades Bar. The majority, 82.8%, of humpback recaptures revealed the sedentary nature of the species, i.e. no movement. Surprisingly, 92% of the roundtail recaptures indicated no net movement. Archer et al. (1985) found roundtail chub to be more mobile than humpback chub in their study of movements in the Black Rocks area. The limitation of the present mark recapture study was that all the effort was confined to Westwater Canyoq which may have biased results toward sedentary individuals. All the multiply recaptured humpback and roundtail chubs displayed no movement including a female roundtail (7F7BIIo829) collected on five occasions (at the Hades Bar site) over the course of 1099 days. DRAFT 39