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• 12 <br />Outside of the spawning season, adult razorback suckers occupy a variety of <br />shoreline and main channel habitats including low runs, shallow to deep pools, <br />backwaters, eddies, and other relatively slow velocity areas associated with <br />sand substrates (Tyus 1987; Tyus and Karp 1989; Osmundson and Kaeding 1989; <br />Valdez and Masslich 1989; Osmundson and Kaeding 1991; Tyus and Karp 1990). <br />Habitat requirements of young and juvenile razorback suckers in the wild are <br />largely unknown, particularly in native riverine environments. Life stages, <br />other than adults, have not been collected anywhere in the Upper Basin in <br />recent times. The last confirmed documentation of razorback sucker juvenile <br />in the Upper Basin was a capture in the Colorado River near Moab, Utah (7aba <br />et al. 1965). <br />The current range of the razorback sucker in the Colorado River extends <br />upstream to Rifle, Colorado. Most razorback suckers captured in the Grand <br />Valley area have been located in flooded gravel-pit ponds adjacent to the <br />river. However, Osmundson and Kaeding (1989) documented razorback sucker <br />movement in various river habitats in the Grand Valley area. Additional <br />surveys since 1988 have documented razorback suckers in riverside ponds as far <br />upstream as river mile 235 near Rifle, Colorado (Burdick 1992). <br />Humpback Chub <br />• Humpback chub generally do not make migrational movements in the upper <br />Colorado River and tend to reside throughout the year within a limited reach <br />of river. Humpback chub are found inhabiting narrow, deep canyon areas and <br />are relatively restricted in distribution. They seldom leave their canyon <br />habitat (U.S. Fish and Wildlife Service 1982). While humpback chub are <br />regularly found dispersed in the Green and Yampa Rivers, the only major <br />populations of humpback chub known to exist in the Upper Basin are located in <br />Black Rocks and Westwater Canyons on the Colorado River. <br />Critical Habitat <br />Critical habitat has been designated within the humpback chub's historical <br />range in the following sections of the Upper Basin (59 F.R. 13374). <br />Colorado, Moffat Countv. The Yampa River from the boundary of Dinosaur <br />National Monument in T. 6 N., R. 99 W., section 27 (6th Principa] <br />Meridian) to the confluence with the Green River in T. .7 N., R. 103 W., <br />section 28 (6th Principal Meridian). <br />Utah, Uintah County: and Colorado, Moffat Countv. The Green River from <br />the confluence with the Yampa River in T. 7 N., R. 103 W., section 28 <br />(6th Principal Meridian) to the southern boundary of Dinosaur National <br />Monument in T. 6 N., R. 24 E., section 30 (Salt Lake Meridian). <br />Utah, Uintah and Grand Counties. The Green River (Desolation and Gray <br />Canyons) from Sumners Amphitheater in T. 12 S., R. 18 E., section 5 <br />• (Salt Lake Meridian) to Swasey's Rapid in T. 20 S., R. 16 E., section 3 <br />(Salt Lake Meridian). <br />