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<br />-17- <br /> <br />The whole river (Table 9) density and biomass estimates (on a unit area basis) <br />in May 1991 generally are slightly lower than the average for the three 1000- <br />foot stations in April 1991. However, that is as expected since two of the <br />three individual (1000 foot) stations represent areas where extensive stream <br />habitat improvement has been completed and the third area has excellent <br />physical habitat for trout as well. In contrast, the whole river population <br />estimate covers all habitat (good and bad) areas in the 12 mile reach of <br />river. Therefore, the whole river estimate(s) of trout/unit area should be <br />lower. <br /> <br />The whole river total trout density and biomass estimates for May 1991 are 67 <br />trout (~ 15 cm)fha and 28.8 kgfha, respectively. The average density and <br />biomass estimates for all trout ~ 15 cm (at the three 1000-foot sites) in <br />April 1991 were 104(ha and 32 kg(ha, respectively. The average density and <br />biomass for all trout ~ 15 cm (at those same sites) in October 1991 were <br />107(ha and 24 kg(ha, respectively. In comparison to other tailrace fisheries <br />in Colorado, these statistics are significantly lower. <br /> <br />As an example, total trout density and biomass for a 2-mile section of the <br />Gunnison River (below Crystal Dam) was 887(ha and 210 kg(ha, respectively. <br />The Gunnison River (like the Dolores) has been subjected to flow depletions <br />since May 1988 (more than 30 months), yet the trout population survived in <br />relatively good condition. However, in the Gunnison River, minimum flows <br />(summer or winter) rarely dropped below 22% ,of the average annual discharge. <br />Contrast this with' the Dolores River below McPhee Dam, where total downstream <br />release for the 1991 water year equates to 17.3% of the 1991 total inflow into <br />McPhee Reservoir. Moreover, the 30 cfs winter flow (October 1990 - March <br />1991) equates to 7.4% of the 1991 water year inflow into McPhee Reservoir and <br />approximately 6% of the average annual inflow. <br /> <br />Fish Trapping ODerations - Julv and August 1991 <br /> <br />Three fish traps were operated for 12 days in July and 10 days in August. <br />There was only 1 day (out of 22 trapping days) when no fish were caught in one <br />or more of the traps. Fish species trapped included brown and rainbow trout, <br />bluehead and flannelmouth suckers, speckled dace, mottled sculpin, roundtail <br />chubs, and green sunfish (see Table SA, Appendix). The vast majority of fish <br />moving into the traps were quite small, predominantly less than 20 cm total <br />length. Only two fish (both rainbow trout) were over 30 cm in length. These <br />two trout (37 and 43 cm) were caught in the trap at river mile 5.5, near <br />Ferris Canyon Campground. <br /> <br />Many rainbow and brown trout, as well as speckled dace and scu1pins, were 6-10 <br />cm total length. This would seem to indicate that the screening of the river <br />was virtually 100% effective. If it were not, it is highly unlikely that we <br />would have captured so many small fish. Seventy-eight fish were captured in <br />the traps. A minimum of 28% (22 of 78) were between 6 and 11 cm (2.4 to 4.3 <br />in.) in length. Not all fish were measured. Only one VI-tagged trout was <br />captured in a trap during the summer. This fish was a 37-cm rainbow that had <br />been tagged in the same segment of the river (river mile 6) immediately below <br />the trap site at river mile 5.5, near Ferris Canyon Campground. <br />