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<br />Bonytail <br />Historical information about the distribution and abundance of bonytail <br />is limited, Jordan (1891) collected one specimen in the Gunnison River and <br />Ellis (1914) collected some bonytail in .the Colorado River near Grand <br />Junction. However, collections during the early 1900's may have confused <br />roundtail chub and bonytail, as they were considered the same species until <br />1970 (Holden and Stalnaker 1970). Holden and Stalnaker (1975) did not collect <br />any bonytail from the upper Colorado River, but Kaeding et al. (1986) reported <br />one specimen from Black Rocks and Valdez (1990) collected 19 specimens <br />tentatively identified as bonytail in Cataract Canyon. The species is <br />extremely rare in the upper Colorado•River basin. <br />METHODS <br />We attempted to document the changes to the Gunnison and Colorado rivers <br />that can be attributed to the Aspinall Unit and the two later projects (Dallas <br />Creek and Dolores). Although changes in streamflow can be readily documented <br />at two long-term USGS gages in the Basin, the precise percentage of change <br />attributable to these projects is difficult to determine. A number of <br />projects in both the Gunnison and Colorado River basins were constructed at <br />the same time as the Aspinall Unit. All of these projects affected the <br />rivers--determining the effect of one project among many is problematic. We <br />were primarily concerned about three major impacts to the Colorado and <br />Gunnison rivers: streamflow (timing and quantity), water temperature, and <br />sediment load. <br />9 <br />