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featured, small, and delicate head and mouth, a slightly overhung snout and subterminal mouth, a small nuchal hump, and a slender body and caudal peduncle. The line extending backwards from the angle of the anal fin passed just over or in front of the upper lobe of the caudal peduncle. Body coloration was typically silvery. Dorsal/anal fin ray counts were usually 9/9 (N = 5), but 8/10 (N = 1), 9/10 (N = 1), and 10/10 (N = 1) were also observed. In comparison, roundtail chub had stouter overall features, including a larger head, a terminal mouth, no nuchal hump, and a more robust body and caudal peduncle. A few roundtail chub > 350 mm TL possessed slightly raised nuchal humps, but the other features just discussed were used to differentiate humpback from roundtail chub. The line extending backwards from the angle of the anal fin passed through the upper lobe of the caudal peduncle. Body coloration was silvery but often darker, especially dorsally. All humpback chubs collected were from the steep-walled upper portion of Whirlpool Canyon in a 1.8-km-long reach beginning at RK 551.8. One additional humpback chub was collected by angling in 2003 in the same reach; it was released before it was tagged. All humpback chub captured were from deep pools or recirculating eddies associated with an upstream riffle, and were typically captured in nets set downstream of large boulders that produced areas with relatively low current velocity. Humpback chub was nearly always captured with roundtail chub and often in the same net set. In autumn 2004, we captured humpback chub, roundtail chub, and bonytail from the same eddy in upper Whirlpool Canyon, which is likely the first such record in many years. We captured humpback chub individuals in each year of the study: two in 2002, four in 2003, and two in 2004. One fish first marked on 6 October 2003 at RK 55 1.8 was recaptured there on 13 October 2003, and then again on 28 July 2004. That fish increased in length from 263 mm TL in 2003 to 297 mm TL in 2004 (34 mm change) and gained 76 grams (136 in 2003 to 212 in 2004) over the capture interval. Another humpback chub captured on 7 October 2003 was recaptured by the Utah Division of Wildlife Resources (S. Finney, pers. comm.) on 29 October 2003 in the same location. Another humpback chub first marked on 23 September 2004 at RK 550.5 was recaptured 0.4 RK upstream in Whirlpool Canyon on 14 September 2005. That 54