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Colorado River basin. Passage of Colorado squawfish and razorback sucker • over manmade barriers might expand the range of these species and aid in their recovery. However, it is not known whether these species will uti- lize a fishway or under what conditions they will use it. 7. The Redlands Diversion Dam on the lower Gunnison River, as currently constructed and operated, is an effective barrier to upstream migration of fishes. Fish can pass downstream over the Redlands Dam, particularly during high flow periods. However, adult fish moving down- stream can also enter the power canal. Fish that enter the power canal may become disoriented and not find their way back into the river. This problem could be magnified if fish migration is reestablished above the dam. 8. The lower 40 to 50 miles of the Gunnison River is histori- cal habitat for Colorado squawfish and razorback sucker. A limited number of adult squawfish are present in the lower Gunnison River, below and above the Redlands Diversion Dam. Adult razorback suckers are more rare in the Gunnison River than are Colorado squawfish. Both species occur in the Colorado River immediately downstream and upstream of the confluence. If Colorado squawfish and razorback suckers utilize a fish passageway at Redlands Dam, they could become reestablished in parts of their historic range. If these fish become reestablished in the river reach above the diversion dam, it is unknown whether these fish will suc- cessfully spawn there. Such a passageway would allow experimentation to determine what type of passage would be best for these species. The facility would be considered a prototype model. If successful, its design might be used in similar situations elsewhere in the upper basin of the Colorado River as a part of the recovery effort for the target species. III. FUNCTIONAL CRITERIA. A. Biological Considerations and Recommended Criteria. 1. Some biological research has been accomplished specifically pertaining to the Colorado squawfish and razorback sucker. However, a larger volume of information pertains to related species. The combination of specific and closely related information should produce reasonably accurate biological criteria. Refer to Appendix A for biological review. 2. Both target species are only moderately strong swirmners, so a fish passage facility should be easily accessible. The majority of the fish are expected to travel upstream in the main channel of the river. This main channel is assumed to be directly downstream of the existing • 4