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( 1 <br />IN] RODUCTION <br />The native fishes found in the Colorado River drainage are a unique group <br />exhibiting a remarkable 740/10 endemism.I Such endemism can be related to the <br />character of the river system itself as it has developed over eons of time. <br />The Colorado River in it's unaltered state is a harsh environment for fish. <br />This large river is bounded for most of it's entire length by steep cliffs, <br />and is characterized by swift, turbulent, muddy water. The river has highly <br />fluctuating flows with accompanying high dissolved salts, heavy sediment <br />loads, and extreme variations in temperature. <br />In recent history, man has altered the basic environment of this large <br />river by irrigation development, dam building, hydro-electric production, <br />increased waste loads, and introduction of exotic fish species. It is be- <br />lieved that as a result of the various river environment changes, that the <br />large river endemic fish species once common throughout the main Colorado <br />River and it's larger tributaries are now confined to the Upper River Basin <br />including the Green River System. The status of these endemic fish in the <br />Gunnison River and the Colorado River in the Grand Junction area is not well <br />known at this time. <br />The Bureau of Reclamation has constructed a number of water development <br />projects in the Upper Colorado River drainage and are presently planning addi- <br />tional projects. In light of the recent concern for endangered and threatened <br />wildlife species, the Bureau of Reclamation entered into a contractural agree- <br />ment with Northwest Fisheries Research (N.F.R.I.) of Clifton, Colorado to <br />conduct a field investigation of the present status of endangered and threatened <br />lEndemism is defined as being native to and restricted to this particular <br />drainage. <br />(1)