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<br />f ~ <br />fishes. A number of participating projects were also built in conjunction <br />with CRSP. The combined operation of these projects has dramatically altered <br />the Colorado River ecosystem, and thus negatively affected the endangered <br />fishes. The Aspinall Unit was completed before passage of the Endangered <br />Species Act; therefore, its effect on native fishes was not considered before <br />construction began. However, the operation of the Aspinall Unit and other <br />CRSP reservoirs continues to effect the endangered fishes, and Section 7 <br />consultation under the Act is required on the Bureau's annual operation of the <br />dams. In addition, two projects--Dolores (McPhee Reservoir on the Dolores <br />River) and Dallas Creek (Ridgeway Reservoir on the Uncompahgre River) were <br />recently constructed on tributaries to the Gunnison and Colorado rivers <br />(Figure 1). These reservoirs did undergo Section 7 consultation, and were <br />built with the stipulation that water from the Aspinall Unit would be used to <br />partially offset the effects of these two projects on the endangered fishes. <br />Studies to evaluate the effects of the operation of Flaming Gorge and Glen <br />Canyon dams on endangered fishes in the Green and lower Colorado rivers are <br />ongoing. The purpose of this document is to: 1) describe changes in the <br />Gunnison and upper Colorado rivers as a result of the Aspinall Unit and the <br />two recent projects, and 2) to hypothesize how these changes have affected the <br />native fish community. This information will be used to design studies to <br />test these hypotheses and to assess the benefits for endangered fishes that <br />could be achieved by modifying the release pattern of the Aspinall Unit. <br />2 <br />