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in samples collected just after impoundment of Flaming Gorge reservoir and was raze in <br />collections made by Holden and Crist (1981) in 1978 to 1980. However, white sucker was <br />relatively common from 1994-1996, particularly in upstream Browns Pazk where water was <br />colder. Razorback X flannelmouth sucker hybrids were detected as early as 1889 in the upper <br />Colorado River basin and as early as 1950 in the upper Green River near Hideout Canyon <br />(Hubbs and Miller 1953), so some level of hybridization of native taxa should be expected even <br />under relatively pristine conditions. However, the variety of hybrid combinations and their <br />abundance in the Green River appears to be a recent phenomenon, as Holden and Crist (1981) <br />reported only a few such hybrids. Specimens of one hybrid sucker combination that we captured <br />appeazed to have traits of white, bluehead, and flannelmouth sucker, which may indicate some <br />level of introgressive hybridization. <br />The relatively high and appazently increasing rate of hybridization noted in this study and <br />in other areas (Holden and Stalnaker 1975a), and the large number of hybrid combinations, <br />suggests that this phenomenon deserves further study and monitoring. Detection of hybrids in <br />field samples will be critical to accurately determine the extent and rates of hybridization. A <br />better understanding of hybridization rates and hybrid fertility, especially in river reaches <br />strongly affected by regulation, may also aid restoration of rare catostomids such as razorback <br />suckers. <br />Drift net sampling.--Nearly all fishes captured in drift net samples were native fishes; <br />only a few non-native white sucker and a single sand shiner larvae were captured. One of the <br />most, surprising results of drift net sampling was the paucity of fish captured. In the nearby <br />Yampa River, drift net sampling conducted in 1994 yielded 124 Colorado pikeminnow larvae <br />and several times that number of individuals of other species, and those totals represent the <br />lowest capture rates recorded from 1990 to 1996 (Bestgen et al. 1998). <br />Water visibility approached 2 m in mid-July in the Green River upstream of the Yampa <br />River for most of the summer in 1994. The exceptionally cleaz water likely allowed fish larvae <br />to maintain positions in low-velocity habitats and avoid downstream transport during conditions <br />32 <br />