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<br />r <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />IV. Study Area: <br /> <br />The study area includes the Gunnison Ri~er from its confluence with the <br />North Fork to its confluence with the Cqlorado River, and the Colorado <br />River from Palisade, CO downstream to t~e Lake Powell inflow area. <br /> <br />V. Study Methods/Approach <br /> <br />I <br />McAda and Kaeding (1991) summarized the major changes to the <br />Colorado rivers resulting from construc4ion and operation of <br />Unit and postulated their effects on th1 endangered fishes, <br />important changes they described are: I <br /> <br />Gunnison and <br />the Aspinall <br />The <br /> <br />1. Reduced water temperature in the Gu nison River within habitat <br />occupied by Colorado squawfish--abo t 20C. Water temperature <br />in the Colorado River is unaffected by the Aspinall Unit. <br /> <br />2. Reduced sediment load in both the C lorado and Gunnison rivers. <br /> <br />3. <br /> <br />Reduced spring runoff in the Gunnis <br />a concomitant increase in fall and <br />monthly flows during May and June, <br />have declined 25 and 32% (respectiv <br />and 12 and 13% in the Colorado Rive <br />Aspinall Unit, <br /> <br />n and Colorado rivers, with <br />inter streamflow. Mean- <br />he primary runoff months, <br />ly) in the Gunnison River <br />as a result of the <br /> <br />McAda and Kaeding (1991) developed nine <br />assess the impact of these changes on th <br /> <br />I <br />ypotheses to guide studies to <br />endangered fishes: <br /> <br />Hypothesis 1. Relative abundance of age-O Colorado squawfish in <br />the Colorado River is greatest duri g years with a natural <br />hydro graph and maximum-annual disch rges of 30,000 to 40,000 <br />cfs (measured at the Cisco stream g gel. Relative abundance is <br />reduced in years with higher or low r maximum-annual <br />discharges, <br /> <br />Hypothesis 2. Length of growing sea on affects over-winter <br />survival of age-O Colorado squawfis <br /> <br />Hypothesis 3. High spring flows and a natural hydro graph reduce <br />non-native fish populations. <br /> <br />Hypothesis 4. The Gunnison River ablve Redlands Diversion <br />contains a small, reproducing Colortdo squawfish population. <br /> <br />Hypothesis 5. Redlands Diversion D~ restricts up and <br />downstream movement of all life stages of Colorado squawfish, <br /> <br />Hypothesis 6. The Gunnison River contains habitat suitable for <br />reintroducing razorback sucker, augmenting the Colorado <br />squawfish population, and establishing a new population of <br />humpback chub. <br /> <br />3 <br />