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-4- Fisherv Monitorine: Studies The Colorado Division of Wildlife (CDOW) began annual fall electrofishing studies on the Dolores River below McPhee Dam in 1986. Results of these surveys provide a comparative data base for ascertaining the impact on the trout fishery resulting from the severe flow reductions implemented in March 1990. In the fall of 1990, the USBOR-DPO requested (through a cooperative agreement) that the CDOW monitor the trout population in the Dolores River through the winter months of 1990/1991. Thus, a cooperative agreement (I-FC-40-10460) was initiated for the purpose of (1) sampling the aquatic invertebrate populations of the Dolores River; (2) monitoring the extent and duration of ice build-up in the river below the dam; and (3) attempting to determine the impact of icing on the trout population. The results of the initial study were summarized and reported previously (Nehring, 1991). Subsequently, the cooperative agreement was modified (Modification No. 001) to cover additional studies during the spring, summer, and early fall 1991. The purpose of the additional study was to collect information on trout growth, movement, density, biomass, age structure, body condition, and mortality. The Cooperative Agreement (Modification No. 001) called for the following: 1. Determine the effects of low summer flows from McPhee Reservoir on the downstream fish population in the Dolores River. 2. Provide information essential for the proper management of downstream releases to protect and enhance aquatic habitat and its associated components. 3. Monitor the anticipated movement of trout due to water flows and temperature changes in the Dolores River from McPhee Dam to Bradfield Bridge. Data collected during the 1991 summer field season provide information needed to satisfy objectives 2, 5, and 6 outlined in the "Dolores Project Resources Optimization Study" document as well as the three study objectives outlined in the modified cooperative agreement. This information should prove helpful to USBOR-DPO in managing future water releases from McPhee Reservoir to minimize any detrimental effects on the fish population. METHODS Studv Area The study area, encompassing 12.2 miles of the Dolores River from McPhee Dam to Bradfield Bridge, was divided into 11 sections varying in length from 0.7 miles to 1.5 miles. Section boundaries, roughly equating to river tuiles below McPhee Dam, are delineated by section lines on USGS topographic maps (Trimble Point, Doe Canyon, and Yellowjacket) covering the area. The study area began at the U.S. Forest Service (USFS) Metaska Campground, approximately 0.6 miles downstream from the dam. Figure 1 (taken from the USGS Dove Creek, Colorado - 1:100,000 scale topographic map) shows the segments of the study area.