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18 <br />1995). No young razorback suckers have been collected in recent times <br />in the Colorado River. <br />There are no current population estimates of razorback sucker in the <br />Upper Colorado River due to low numbers captured in recent years. <br />Analygia of Sn i a/ ri i -1 H^hi - ik y to be Affe['t PA <br />Osmundson and Kaeding (1989) found that 76 percent of t:he razorback <br />suckers captured in the Colorado River between 1979 and 1985 were <br />captured in the Grand Valley area. Results of surveys conducted <br />during May and June of 1986-1988 indicate that areas within the <br />15-mile reach may be concentration points for the razozback sucker <br />during spring runoff. Male and female razorback suckers in spawning <br />condition have been found in the 15-mile reach, although no larvae or <br />juveniles have been found. Although data is limited, 1-adio-telemetry <br />studies led Oamundson and Kaeding (1989) to conclude that razorback <br />suckers may move into the 15-mile reach to spawn in thc: spring, but <br />most spend the remainder of the year in a 18-mile reach downstream <br />from the confluence of the Gunnison River. <br />The current range of the razorback sucker in the Colorado River <br />extends upstream to Rifle, Colorado. Most razorback suckers captured • <br />in the Grand Valley area have been located in flooded gravel-pit ponds <br />adjacent to the river. However, Osmundson and Kaeding (1989) <br />documented razorback sucker movement in various river habitats in the <br />Grand Valley area. They documented razorback suckers i-n the 15-mile <br />reach as far upstream as river mile 163.6. Additional surveys since <br />1988 have documented razorback suckers in riverside po:ids as far <br />upstream as river mile 235 near Rifle, Colorado (Burdic:k 1992). <br />The humpback chub is a medium-sized freshwater fish (less than 500 mm) <br />of the minnow family. The adults have a pronounced dorsal hump, a <br />narrow flattened head, a fleshy snout with an inferior--subterminal <br />mouth, and small eyes. It has silvery sides with a brown or olive <br />colored back. <br />The humpback chub is endemic to the Colorado River Bassin and is part <br />of a native fish fauna traced to the Miocene epoch in i'ossil records <br />(Miller 1946; Minckley et al. 1986). Humpback chub remains have been <br />dated to about 4000 B.C., but the fish was not described as a species <br />until the 1940's (Miller 1946), presumably because of :Lts restricted <br />distribution in remote white water canyons (USFWS 1990b). Because of <br /> <br />