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was the most abundant introduced fish captured in eddies that yielded <br />humpback chub. <br />During September 1989, flows in Yampa Canyon were reduced to less <br />than 2.83 m3/s and fish habitat was limited to shallow riffles (about 15 <br />cm depth), and deeper pools and runs (about 1 m depth). On September 7, we <br />collected five chubs (four roundtail chubs and one suspected roundtail <br />chub X humpback chub hybrid) and seven channel catfish in pools and <br />eddies (about 1 m deep) in Big Joe Rapid (km 38.4). Other chubs, including <br />a suspected humpback chub, were observed about 0.8 km upstream in a <br />1.1-m-deep pool created by shoreline boulders. No fish were observed or <br />collected in the vicinity of Warm Springs Rapid (km 6.4) on September 14. <br />Discussion <br />Humpback chub were distributed in Yampa Canyon from km 72 to its <br />confluence with the Green river at Echo Park, and in Whirlpool Canyon of <br />the Green River (Figure 1). The fish has also been reported just upstream <br />of Yampa Canyon in Cross Mountain Canyon and the lower portion of the <br />Little Snake River (E. Wick, Colorado State University, personal <br />communication). Humpback chubs were primarily captured in canyon-bound, <br />moderate to steep-gradient reaches where the river was somewhat turbulent <br />and deep. <br />Humpback chub were rare in DNM (<I% total catch) and represented only <br />870 of all chub captures. However, capture of 133 fish, including 29 <br />juveniles, indicated that Yampa Canyon supports a small but reproducing <br />population of humpback chub. Although we recognize that sampling <br />techniques in earlier studies in Yampa Canyon were different from ours <br />(e.g., Banks 1964; Vanicek et al. 1970; Holden and Stalnaker 1975a, 1975b; <br />12