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that the mean monthly flows fall within the ranges listed above with the <br />desired frequency such that, over time, the mid-point between the low and <br />high end of each range is the targeted flow. Thus, during some years, mean <br />flows would be in the upper end of the range, in other years, the lower <br />end; the result would be a long-term average in the middle of each range. <br />Although a return of the spring hydrograph to its historic level would be <br />the safest recommendation to assure recovery, we do not believe it is <br />necessary. On the other hand, current spring flows are inadequate: the. <br />squawfish population has apparently declined since historic times and the <br />razorback sucker population is practically extirpated. Obviously, main- <br />taining the status quo will not be enough. Based on existing data and our <br />current state of knowledge, we believe that meeting the above recommenda- <br />tions will be the minimum necessary to reverse the decline of these popu- <br />lations and bring about recovery. <br />WINTER FLOWS (NOVEMBER-FEBRUARY) <br />Genera <br />Optimum winter flows for the Colorado squawfish and razorback sucker in <br />the 15-mile reach are difficult to estimate. As discussed above, high <br />flows during spring are critical in shaping the river channel, in deter- <br />mining substrate composition, and in influencing the abundance of various <br />species for the remainder of the year. Both spring and summer flows are <br />critical in influencing quality and quantity of spawning habitat for the <br />two species. Summer flows are important in providing good feeding and <br />resting habitat at a time when metabolic demands, activity, and growth are <br />47