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4 <br />Critical Habitat <br />Critical habitat has been designated within the 100-year floodplain of the <br />Colorado squawfish's historical range in the following sections of the Upper <br />Basin (59 F.R. 13374). <br />Colorado, Moffat County. The Yampa River and its 100-year floodplain <br />from the State Highway 394 bridge in T. 6 N., R. 91 W., section I <br />(6th Principal Meridian) to the confluence with the Green River in <br />T. 7 N., R. 103 W., section 28 (6th Principal Meridian). <br />Colorado. Moffat Countv. The Green River and its 100-year floodplain <br />from the confluence with the Yampa River in T. 7 N., R. 103 W., <br />section 28 (6th Principal Meridian) to the confluence with the Colorado <br />River in T. 30 S., R. 19 E., section 7 (Salt Lake Meridian). <br />Colorado. Rio Blanco Countv: and Utah. Uintah Countv. The White River <br />and its 100-year floodplain from Rio Blanco Lake Dam in T. 1 N., <br />R. 96 W., section 6 (6th Principal Meridian) to the confluence with the <br />Green River in T. 9 S., R. 20 E., section 4 (Salt Lake Meridian). <br />Colorado. Delta and Mesa Counties. The Gunnison River and its 100-year <br />floodplain from the confluence with the Uncompahgre River in T. 15 S., <br />R. 96 W., section 11 (6th Principal Meridian) to the confluence with the <br />Colorado River in T. 1 S., R. 1 W., section 22 (Ute Meridian). <br />and Garfield Counties. The Colorado River and its 100-year floodplain <br />from the Colorado River Bridge at exit 90 north off Interstate 70 in <br />T. 6 S., R. 93 W., section 16 (6th Principal Meridian) to North Wash, <br />including the Dirty Devil arm of Lake Powell up to the full pool <br />elevation, in T. 33 S., R. 14 E., section 29 (Salt Lake Meridian). <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 311 Bridge in <br />T. 29 N., R. 13 W., section 17 (New Mexico Meridian) to Neskahai Canyon <br />in the San Juan arm of Lake Powell in T. 41 S., R. 11 E., section 26 <br />(Salt Lake Meridian) up to the full pool elevation. <br />Biology <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 />