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Recommendations <br />Availability of good winter habitat has probably not been a limiting <br />factor for adult Colorado squawfish or razorback sucker in the upper <br />Colorado River. We believe the decline of these populations is in part <br />related to the reduction of spring flows, as discussed previously. Unlike <br />spring flows, mean monthly flows during winter have actually increased <br />since historic times (Table 11 and Fig. 14). We are not aware of negative <br />effects on the endangered fishes that may have resulted from these in- <br />creased flows. Though average velocities increase with higher flows, there <br />is probably an adequate number of low-velocity pools, runs, and micro- <br />habitats available at present winter discharge levels. Whether the in- <br />crease in flows has had a beneficial effect on winter habitats of the rare <br />fish in the 15-mile reach is not known. One possible benefit of higher <br />flows would be the increased availability of large backwaters for use by <br />Table 11. Summary of recent and historic discharge for the Colorado River <br />at the top of the 15-mile reach during the months of November-March. <br />Values are means of monthly means for period of record (data from Appendix <br />Table VI). <br />Years No. years NOV DEC JAN FEB MAR <br />Recent <br />1954-1989 36 2,161 1,889 1,765 1,781 2,006 <br />(SD) (492) (420) (368) (409) (541) <br />Historic <br />1902-1942 41 1,789 1,414 1,322 1,346 1,786 <br />(SD) (317) (248) (195) (194) (459) <br />Recent/historic 121% 134% 134% 132% 112% <br />49