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1 <br />Cataract Canyon Stock <br />The humpback chub stock in Cataract Canyon is small but appazently stable based on the presence of <br />juvenile fish (Valdez 1990). The trend of stability should be expected to continue in this remote <br />location since few human activities should affect the population. <br />Colorado Pikeminnow: The interim management objective for adult Colorado pikeminnow estimated <br />population size in the upper Colorado River basin is 5477 (± 966) per stock (Lentsch et al 1998). <br />Yampa/Green River Stock <br />The Yampa/Green River stock of Colorado pikeminnow is stable based on the numbers of adults (n = <br />145) captured in the Yampa River between 1981 and 1988 and the collection of larval and postlarval <br />pikeminnow that demonstrates successful reproduction is occurring in the river (Tyus and Karp <br />1989). The estimated population is approximately 1400. The downstream drift of larval <br />pikeminnow from the Yampa River spawning area suggests that the fish must move a long distance <br />upstream to repopulate upstream azeas on the Yampa that aze used for the nonspawning period of the <br />year (Tyus 1986). Colorado pikeminnow probably return to the Yampa River as sub-adults because <br />only 3% of 198 fish collected in the Yampa were juveniles (Tyus and Karp 1989). <br />Desolation-Gray Canyon Stock <br />The Colorado pikeminnow in the Desolation -Gray Canyons is estimated at 1,000 adults and <br />considered stable with successful reproduction and recruitment indicating that the stock is self- <br />sustaining. <br />Upper Colorado River Stock <br />The Colorado pikeminnow stock in the reach of the Colorado River downstream from Grand <br />Junction, Colorado, is approximately 600 and increasing. During standazdized surveys of the Upper <br />Colorado River between RK 212.5 and 247.9, an average of 3 adult Colorado pikeminnow were <br />captured annually between 1979 and 1981 or 0.16 fish per kilometer of river (Osmundson and <br />Kaeding 1989a). The mean catch per unit of effort for subadult and adult Colorado pikeminnow by <br />electrofishing between 1987 and 1992 has been relatively stable (an average of about 0.2 fish per <br />hour) with a high peak of slightly more than 1 fish per hour in 1991(McAda et al. 1993; 1994). <br />The Interagency Standazdized Monitoring Program provides data on Colorado pikeminnow for two <br />reaches of the Colorado River (Reach 7: RK 159 - RK 138 and Reach 8: RK 109 - RK 79). The <br />catch per unit of electrofishing for subadult and adult Colorado pikeminnow in Reach 7 averaged <br />slightly over 0.3 fish per hour between 1986 and 1992 (McAda et al. 1993). The catch in 1992 was <br />over 1 fish per hour that was about three times greater than the average. The catch per unit of <br />electrofishing for subadult and adult Colorado pikeminnow in Reach 8 averaged 0.59 fish per hour <br />between 1986 and 1992 (McAda et al. 1993). The catch in 1992 in Reach 8 was about 1.9 fish per <br />hour that was nearly four times the average. <br />i] <br />t <br /> <br />t <br />12 <br />