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<br />Under the alternatives to construct the passageway, no significant impact on wildlife species is <br />projected due to the small acreage involved with the fish passageway and due to plans to replace <br />vegetation losses. <br /> <br />It is recognized that altered operation of the Aspinall Unit can affect fisheries in Blue Mesa <br />Reservoir and in the Gold Medal trout fishery downstream. The proposed interim water <br />agreement will involve releases of water from the reservoir and maintenance of these flows past <br />the Redlands Diversion Dam. These changes are shown in Tables 1 through 4 on pages 21, 23, <br />and 24, and in Appendix E. Resultant effects on fish and wildlife resources will not be <br />significant under Alternatives A and B because changes in river flows and reservoir content are <br />minor in most years as can be seen from the tables. In a series of dry years exemplified by <br />1990, the reduction in Blue Mesa Reservoir's water content could reduce productivity of the <br />reservoir. Presently, Colorado State University is conducting studies on the reservoir limnology <br />and the relationship between reservoir productivity and operations; and this information will help <br />in the development of a long-term water contract. There will be some benefits to the trout <br />fishery in the Black Canyon and Gunnison Gorge areas as low summer flows would occasionally <br />be supplemented over existing conditions. <br /> <br />Improved flow regimes in the Gunnison River downstream from the Redlands Diversion Dam <br />in low flow periods will benefit both terrestrial and aquatic resources down to the confluence <br />with the Colorado River by better supporting associated riparian vegetation communities and <br />increasing the wetted perimeter of the river channel. <br /> <br />Endan!!ered Suecies <br /> <br />Existinl! Conditions <br /> <br />The large rivers of the Upper Colorado River Basin are home for four native fish species that <br />are listed as endangered under the Endangered Species Act. This means that the fish are in <br />danger of extinction. The four fish are the Colorado squawfish (Ptychocheilus lucius) , the <br />razorback sucker (Xyrauchen rexanus), the humpback chub (Gila cypha), and the bonytail chub <br />(G. elegans). A variety of factors--diversion of flows, introduction of non-native species, <br />floodplain alterations, barriers to migration, and water quality-have significantly changed the <br />rivers these fish live in and their numbers have dropped sharply. In the Gunnison River (McAda <br />and Kaeding, 1991) flows have been depleted and the naturally occurring high spring flows have <br />been reduced. The RelIlands Diversion Dam has cut off migrations of fish from the Colorado <br />River into the Gunnison as seen by the relatively large numbers of fish that congregate <br />downstream from the dam and the low numbers upstream. <br /> <br />Various sources indicate that the Colorado squawfish and razorback suckers were once common <br />in the Gunnison River from the Delta area to Grand Junction (Kidd, 1977; Chamberlain 1946; <br />and Osmundson and Kaeding, 1989). Quartarone (1993) presents several local historical <br />accounts on the abundance of Colorado squawfish and razorback suckers in the Gunnison River <br /> <br />27 <br />