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<br />f <br /> <br />and spawning. Thus, lower and more stable winter flows are considered habitat <br />requirements of razorback sucker. <br /> <br />RECOMMENDATIONS <br /> <br />Flow and Temperature <br /> <br />Decline and endangerment of the Colorado River fishes is due, in part, to <br />human-induced habitat changes. Closure and operation of Flaming Gorge and <br />Fontene1le dams on the upper Green River changed aquatic habitats (Pearson <br />1967) and eliminated most of the native fishes in 128 km of river above DNM <br />(Baxter and Simon 1970; Vanicek et al. 1970). Current operations of Flaming <br />Gorge do not provide desirable flow and temperature conditions for downstream <br />native fish populations. Standing crops of endangered fishes in the Green <br />River below its confluence with the Yampa River are presumably being <br />maintained by the more natural flow and temperature regimens of the Yampa <br />system ("Holden 1978; Tyus and Karp 19B9) and by the mitigating effects of <br />other tributary flows further downstream. <br /> <br />Miller et al. (1982c) provided some flow recommendations for Colorado <br />squawfish in the Green River which considered survival, rather than <br />maintenance or recovery, of self-sustaining populations. These investigators <br />recognized that additional flows were needed to maintain endangered fish <br />habitat, but could not identify them because of limited information. Operation <br />of Flaming Gorge Dam can be altered to aid recovery of the endangered <br />Colorado River fishes. Efforts to coordinate timing of key Green (via <br />operation of Flaming Gorge Dam) and Yampa river flow events should be <br />explored for recovery of the rare fishes in the Green River basin. <br /> <br />Two major changes may be necessary in Flaming Gorge operations to provide <br />acceptable flows and temperatures for the endangered fishes: higher and <br />warmer spring releases, and lower, more stable flows during the remainder of <br />the year. We recommend that the following flow regimes be provided and <br />evaluated for recovery of the target fishes: <br /> <br />SDrinQ (March 21-June 21) <br /> <br />We recommend that Flaming Gorge releases be increased in average and high <br />water years (about 70% of the years) to pattern spring flows of the Yampa <br />River, Darticu1arly with respect to timing and duration. Maximum streamflow of <br />113.2 m3/s or more of warmest available water (highest lake levels) would <br />provide needed fish habitat. These releases should be synchronized with Yampa <br />River spring runoff, and occur for a period of ab~ut three to six weeks, <br />resulting in an average flow in excess of 367.9 m ~s at Ouray, Uta~ (sum of <br />average peak flow at mouth of Yampa River, 254.7 m Is, and 113.2 m Is released <br />from Flaming Gorge Dam). This flow should be followed by flows of at least <br />56.6 m3/s for an additional week. Bottom1ands in the Jensen and Ouray areas <br />would thereby be flooded, but fish access to these areas may need improvement. <br />Water temperatures during Colorado squawfish migrations (May 23 to July 22) <br />should range from 140C to about 220C. Water temperatures in the Ouray reach <br />should be at least 200C by June I. <br /> <br />31 <br />