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Habitat Classif cation Although the habitat classifications are adequate to represent the types of habitats found in the study areas, they are not adequate to represent habitats in other areas where Colorado pikeminnow maybe found, such as the Grand Valley of the Colorado River, or the San Juan River. Therefore, if these habitat classifications are to be used in the future for other research projects they will have to be modified by the addition of more habitat descriptions. Future Study - There is considerable informative data concerning backwater use by the remaining Green River fish community still available in this data set. Resources should be allocated for the continued analyses. RESOLUTION OF DISCREPANCIES Nonnative C rinids yP Due to the different geomorphological characteristics of the Ouray and Mineral Bottom reaches, high flows affected the nonnative cyprinids differently. In Ouray, when spring peak flows were greater than bar top but less than bankfull (475 m3/s [16775 cfsJ), low velocity habitat was completely unavailable. The net effect was a decrease in nonnative cyprinids in the years of 1990-1992 and 1994. However, when peak flows exceeded bankfull, the net effect was an increase in nonnative cyprinids, presumably due to the large area of flooded bottomland that becomes available at greater than bankfull flows (1993, 1995-1996). This increase may be attributed partly to the low velocity refuge, which may prevent downstream displacement of the fish, and to increased reproductive activity in the flooded bottomlands However, near Mineral Bottom, nonnative cyprinids were negatively correlated with high flows at the Green River, at Green River gage. In this canyon-bound restricted meander reach, over-bankfull flows are much higher (> 850 m3/s [30000 cfs]), and at no time during the study did these flows occur. Nonnative cyprinid catch rates at Mineral Bottom were consistently lower than at Ouray, but with much less variation and relatively small high-flow decreases. One explanation for the limited high-flow effect maybe the small but steadily increasing amount of flooded tributary habitat that is available at flows greater than 198 m3/s (6990 cfs), which was exceeded each year of the study. This suggests that control of nonnative cyprinids could be affected by the implementation of peak flows at slightly less than bankfull, without compromising the availability of habitat at base flow, a critical period for Colorado pikeminnow. However, this would be detrimental to the recovery of razorback sucker, which requires overbank flooding of bottomlands. xxi