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Based on calculations by OSM, the proposed action will result in a net average • annual water depletion of 149.3 acre-Feet from the Yampa River due to surface run-off control and sediment control. Conservation measures, outlined later in this document, are necessary to offset the likelihood of jeopardy For federally listed fishes which may be impacted by project-related water depletions. BASIS FOR OPINION COLORADO SQUAWFISN Early records indicate that the Colorado equawfieh was once abundant throughout the Colorado Rlver system. It was abundant over all of its range prior to the 1850'e (Seethaler, 1978). The present range of the Colorado equawfieh is restricted to the upper Colorado River basin. It is found inhabiting about 345 miles of the mainetem Green River from the mouth of the Yampa River downstream to the confluence of the Crean and Colorado Rivera. Its range also extends 150 miles up the Yampa River and 156 miles up the White River, the two major tributaries of the Green River. In the mainetem Colorado River, it is currently found from Lake Powell extending about 201 miles up- stream to Palisade, Colorado, and in the lower 33 miles of the Gunnison River, a tributary to the mainetem Colorado River (Fish and Wildlife Service, 1982). Decline of the populations of the Colorado equawfieh correlates very closely • with the construction of dame and reservoirs and the removal of water from the Colorado River eye tem. Colorado equawfieh evolved in and apparently require stream habitat conditions typified by great seasonal fluctuations in flow and turbidity, coupled with warmer water temperatures in the summer. Additionally, it appears that equawfieh require relatively unrestricted movement to satisfy all of their life history requirements. Movement of adult equawfieh appears to be related to flow, temperature, feeding and spawning behavior. The life stages that appear to be moat critical are from egg fertilization through ire first year of life. It hoe been demonstrated that these phases of Colorado equawfieh development are also closely tied to some specific habitat requirements. It ie imperative that proper flows and temperatures are provided during these essential life stages. The conservation measures outlined below will help further investigate and meet the habitat tequitemente of the Colorado equawfieh, thus offsetting project- related impacts and the likelihood of jeopardy for the species. . HUMPBACK CHUB Humpback chub generally do not make migrational movements in the upper Colorado River and tend to reside throughout the year within a limited reach of river. Humpback chub are found inhabiting narrow, deep canyon areas, and are relatively restricted in distribution. They seldom leave their canyon habitat (FWS, 1982). Humpback chub are still occasionally found dispersed in the Green and Yampa Rivera, although little ie known about the distribution • and abundance of the species in these rivers. The only major populations of 2