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<br />. <br /> <br />. <br /> <br />. <br /> <br />MAY-15-199B 15:48 <br /> <br />BOR LULND <br /> <br />9706633212 P.07/24 <br /> <br />6 <br /> <br />New Mexico. San Juan County: and Utah. San Juan County. The San Juan <br />River and its 100-year floodplain from the State Route 371 Bridge in <br />T. 29 N., R. 13 W., section 17 (New Mexico Meridian) to Neskahai Canyon'in <br />the San Juan arm of Lake Powell in T. 41 S., R. 11 E., section 26 (Salt <br />Lake Meridian) up to the full pool elevation. <br /> <br />BioloGV <br /> <br />The life-history phases that appear to be most critical for the Colorado <br />squawfish include spawning, egg fertilization, and development of larvae <br />through the first year of life. These phases of Colorado squawfish <br />development are tied closely to specific habitat requirements. Natural <br />spawning of Colorado squawfish is initiated on the descending limb of the <br />annual hydrograph as water temperatures approach 20 .C. Spawning, both in the <br />hatchery and in the field, generally occurs in a 2-month timeframe between <br />July 1 and September 1, although high flow water years may suppress river <br />temperatures and extend spawning in the natural system into September. <br />Conversely, during low flow years when the water warms earlier, spawning may <br />occur in late June. ' <br /> <br />Temperature also has an effect on egg development and hatching. In the <br />laboratory, egg mortality was 100 percent in a controlled test at 13 'C. At <br />16 'C to 18 'C, development of the egg is slightly retarded, but hatching <br />success and survival of larvae was higher. At 20 'C to 26 'C, development and <br />survival through the larval stage was up to 59 percent (Hamman 1981). <br />Juvenile temperature preference tests showed that preferred temperatures <br />ranged from 21.9 'C to 27.6 'C. The most preferred temperature for juveniles <br />and adults was estimated to be 24.6 'C. Temperatures near 24 'C are also <br />needed for optimal development and growth of young (Miller et al. 1982). <br /> <br />Only two Colorado squawfish confirmed spawning sites, as defined in the <br />Colorado Squawfish Recovery Plan, have been located in the Basin: river <br />mile 16.5 of the Vampa River and river mile 156.6 of the Green River. These <br />areas have the common characteristics of coarse cobble or boulder substrates <br />forming rapids or riffles associated with deeper pools or eddies. It is <br />believed that a stable, clean substrate is necessary for spawning and <br />incubation. Substrates are swept clean of finer sediments by high flows <br />~couring the bed prior to the spawning period. <br /> <br />O'Brien (1984) studied the hydraulic and sediment transport dynamics of the <br />cobble bar within the Vampa River spawning site and duplicated some of its <br />characteristics in a laboratory flume study. Based on field observations, he <br />reported: <br /> <br />"On the rising limb of the hydrograph, sands are deposited in the <br />cobble interstices. These sands are interchanged between the bed and <br />the suspended zone for discharges less than bankfull. Depending on <br />the supply-capacity relationship, either deposition or scour could be <br />occurring. When the cobbles move, the sand, of course, is washed from <br />the interstices and may be completely remoyed from around the cobbles. <br />Rearrangement of the cobbles will result in more stability of the <br />