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• BASIS FOR OPINION COLORADO SQUAWFISA Early records indicate that the Colorado squawfish was once abundant throughout the Colorado River system. It vas abundant over all of its range prior to the 1850's (Seethaler, 1978). The present range of the Colorado squavfish is restricted to the upper Colorado River basin. It is found inhabiting about 345 miles of the main stem Green River from the mouth of the Yampa River dovnstream to the confluence of the Green and Colorado Rivers. Its range also extends 140 miles up the Yampa River and 156 miles up the White River, the tvo major tributaries of the Green River. In the mains[em Colorado River, it is currently found from Lake Powell extending about 201 miles upstream to Palisade, Colorado, and in the lower 33 miles of the Gunnison River, a tributary to the mainstem Colorado River (Fish and Wildlife Service, 1982). Ij Decline of the populations of the Colorado squavfish correlates very closely vith the construction of dams and reservoirs and the removal of water from the Colorado River system. Colorado squawfish evolved in and apparently require stream habitat conditions typified by great seasonal fluctuations in floe and turbidity, coupled vith warmer eater temperatures in the summer. • Additionally, it appears that squavfish require relatively unrestricted movement to satisfy all of their life history requirements. Movement of adult squawfish appears to be related to floe, temperature, feeding and epavning behavior. The life stages that appear to be most critical are from egg fertilization through its first year of life. It has been demonstrated that these phases of Colorado squawfish development are also closely tied to some specific habitat requirements. It is 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 requirements of the Colorado squavfish, thus offsetting project-related impacts and the likelihood of jeopardy for the species. HUPQ'BACK 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. Aumpback chub are found Inhabiting narrow, deep canyon areas, and are relatively restricted in distribution. They seldom leave their canyon habitat (FWS, 1982). While the humpback chub are still occasionally found dispersed in the Green and Yampa Rivers, the only major populations of humpback chub conclusively known to exist in the Upper Colorado River Basin are located in Black Rocks and Westvater Canyons on the Colorado River. • Conservation measures outlined below viii contribute to providing proper habitat conditions for humpback chub, thus offsetting the likelihood of jeopardy for the species. 2