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-33- 4. 51,000 AF of water passed down the river during the 1991 water year, yet the trout fishery showed a large decline from October 1991 compared to October 1990. This is a strong indication of the inadequacy of the 25,400 AF pool of water for "fishery and aesthetic purposes". Research in other areas in Colorado and on other streams throughout the western U.S. indicate that 20%-30% of the average annual discharge (AAD) is the minimum flow that can sustain a co1dwater stream ecosystem for a calendar year or longer. The AAD into McPhee Reservoir is 350,000 AF. Thus, 70,000 AF is the minimum amount of water (on an annual basis) needed to keep the Dolores River tailrace fishery from collapsing. Recommendations Future Studies: There are many unanswered questions that continued study through 1992 and 1993 could help answer regardless of the flow regime during the summer of 1992 (and 1993). 1. Spring and fall e1ectrofishing studies (at the three 1000-foot stations under study since 1986) should continue through 1992 and 1993 to document the rate and level of recovery of the trout population. In addition, a whole river trout population estimate should be completed in April or May 1992 to monitor the recovery of the trout population throughout the 12+ mile reach of river from Metaska Campground down to Bradfield Bridge. 2. Tagging studies (during e1ectrofishing operations) should continue to increase the number the marked trout at large throughout the river. These tagging studies will provide an increasing base of knowledge on trout growth rates, mortality rates, and movement that can be used to better define critical levels of streamflow and water temperature during the most stressful part of the year. 3. Additional fish trapping studies could be continued once the run-off season (and any accompanying "spill") is over. Since the fish traps are already constructed and materials acquired, the traps can be quickly installed and maintained if there is a desire to continue to study trout movement in relation to thermal stress and streamflow regimes. However, it is unlikely there will be significant measurable movement of trout (a mile or more) unless summertime discharge levels are in the 70-80 cfs range and we experience a few weeks of daytime high air temperatures of 95-1050 F in the Dolores River corridor. At flows of 50-60 cfs (concurrent with daytime high air temperatures of 95-1050 F), we would most likely have movement of trout into the traps, i.e., attempting to move upstream to cooler water. However, it is unlikely the trout would be able to negotiate the large number of shallow riffles (2-4 inches deep).