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<br />-19- <br /> <br />recaptured during electrofishing studies in August or October. Perhaps <br />significantly, all four trout were recaptured in deep pool and/or run sections <br />of river immediately downstream from one of these blocking riffle areas. <br /> <br />More than 475 trout (including 289 brown, 157 rainbow, and 30 cutthroat) were <br />tagged with VI tags between April 1 and October 4, 1991. During that time, 20 <br />rainbow, 5 cutthroat, and 33 brown trout with VI tags were recaptured. One <br />trout was recaptured during the fish trapping operation, five were recaptured <br />by fly fishing, and 52 were recaptured during electrofishing operations. <br />Fourteen VI tagged trout were captured three times during the study period. <br /> <br />In all, there were 72 instances where VI tagged trout were recaptured between <br />May 13 and October 4, 1991. A very small percentage of the tagged recaptured <br />trout had moved out of the original river segment where they were tagged. <br />Eighty-five percent of the recaptures occurred within the same river segment <br />where tagging took place. Only 17% of the trout (5 brown, 1 cutthroat, and 4 <br />rainbow trout) moved one river segment (0.7 miles) or more between the time of <br />initial tagging and recapture. <br /> <br />There were seven instances of downstream movement and four instances of <br />upstream movement. The farthest downstream movement was six river,segments <br />(from segment 1 to segment 7). The farthest upstream movement was four river <br />segments (from segment 6 to segment 2). Nine of the ten trout moving more <br />than one river segment were initially tagged during the whole-river-boat- <br />shocking operation between May 13 and 16, 1991, coincident with the beginning <br />of the managed "spill" of McPhee Reservoir. It is quite probable that much <br />(if not all) of the movement that occurred (both upstream and downstream) took <br />place during the spill period. This conclusion is supported by the results of <br />the fish trapping operations in July and August 1991. <br /> <br />Biologv of the Dolores River Trout-Species and Population Responses <br /> <br />The CDOW's management objective for the Dolores River (below McPhee Dam) is <br />the creation and maintenance of a cold water-basic yield-high quality trout <br />fishery with a trophy trout component. Given an adequate water supply, the <br />Dolores River below McPhee Dam has the potential to grow trout to a large size <br />(16-20 in.) in 3 to 4 years of life. The CDOW's management plan recognizes <br />fluctuations in release patterns dictated by the Dolores Project operating <br />criteria may preclude the establishment of a wild (self-sustaining, naturally <br />reproducing) trout population in the Dolores River downstream from McPhee Dam. <br />Therefore, it is likely there may always be a need to stock some fingerling or <br />subcatchable trout to sustain this fishery. This may certainly be true for <br />rainbow trout. <br /> <br />Nonetheless, in its 3 years study plan, the USBOR-DPO (in the Dolores Project <br />resources optimization study plan) committed to: "Provide constant releases <br />seasonally to determine the requirements for successful trout spawning. <br />Measure success through subsequent fish sampling." In light of this <br />commitment, this section of the report is included to facilitate the <br />achievement of the 3-year study plan objectives. <br />