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Spawzzing Colorado pikeminnow A concentration of spawning Colorado pikeminnow was sampled at the Rabbit Valley (RK 238) site in 1994 and 1995. Of the 39 pikeminnow handled in those two nights of sampling, the overwhelming majority (89.7%) were ripe males with only two suspected females captured. Unproductive sampling in adjacent locations suggest the results at Rabbit Valley were indicative of a concentration area, not simply fish moving to another location. Rabbit Valley is located 12.8 km downstream of Three Fords Rapid. In 1995, five of the 28 fish collected were recaptures; two of those five were originally tagged at RK 446.6 and 480.1 in the Uintah Basin, i.e. these fish at some point in time moved downstream and past the Three Fords area to be captured at Rabbit Valley. In 1994 and 1995, similar sampling at the Coal Creek site, located just 4.8 km downstream of Rabbit Valley yielded one pikeminnow each year. We suspect that Colorado pikeminnow spawning still occurs at the Three Fords site, (previously identified as a spawning site (Tyus et al. 1987)). However, spawning occurs at other locations in the vicinity. During the 1997 monitoring trip, sampling at Joe Hutch (RK 256) on 18 July revealed the greatest concentration of adult Colorado pikeminnow (n=44) ever observed in Deso/Gray. Of that total, 36 pikeminnow were ripe males (88%); two were immature (6%) ; one was a female (940 mm TL) and one was a suspected female. Monitoring at Joe Hutch (eleven occasions since 1985; located 6.4 river kilometers upstream of Three Fords) had never revealed a concentration of adult pikeminnow even when sampling the following night at Rabbit Valley has. Despite specific sampling at flat Canyon and Dripping Springs a new spawning area in Deso/Gray was not found. However, the Three Fords spawning area was better defined. Spawning appears to occur in upper Gray Canyon throughout an 18 km stretch of river extending from RK 256 to 238 with the focus of spawning activity shifting within this area on an annual basis (Figure 16). Sympatric species Trends in flannehnouth and Bluehead sucker catch rates differed greatly (Report C; Appendix Figure 2). Since 1989, flannelmouth suckers were collected at each trend site with only two exceptions: RK 280.5 in 1991 and again in 1996. Trends in the flannelmouth sucker catch rate has followed a similar pattern to that of the chubs, with relatively high catch rates recorded in 1989 followed by a general decline throughout the canyon through the 1994 sampling trip. In 1995, CPE increased dramatically at all sites with the greatest site CPE recorded at RK 295.7. Electrofishing also produced large catches of juvenile flannelmouth suckers in 1994 (n=122) and 1996 (n-175). A length frequency analysis for flannelmouth suckers indicates poor recruitment of juvenile flannelmouth sucker through 1993. Beginning in 1994 and continuing through 1996 population structure looked healthier. Flannelmouth sucker reproduction, as indexed by YOY catch rates, was remarkably consistent from 1992 through 1995 and appeared to increase in 1996. Bluehead suckers were more spottily distributed in Deso/Gray; absent from 25% of the trend site samples since 1992. Bluehead suckers were more common in the upper reaches of Deso/Gray canyons (Report C; Appendix Figure 2). Average annual net catch rates were lowest in 1990 (0.009) and greatest in 1994 (0.08). As with the flannelmouth suckers, blueheads xvii