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<br />16 <br /> <br />1986-1988 indicate that areas within the 15-mile reach may be concentration <br />points for the razorback sucker during spring runoff. Male and female <br />razorback suckers in spawning condition have been found in the 15-mile reach. <br />although no larvae or juveniles have been found. Although data is limited. <br />Osmundson and Kaeding (1989) think razorback suckers may move into the 15-mile <br />reach to spawn in the spring, but most spend the remainder of the year in an <br />18-mile reach downstream from the confluence of the Gunnison River. <br /> <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. They documented <br />razorback suckers in the 15-mile reach as far upstream as river mile 183.6. <br />Additional surveys since 1988 have documented razorback suckers in riverside <br />ponds as far upstream as river mile 235 near Rifle. Colorado (Burdick 1992). <br /> <br />Humpback Chub <br /> <br />The humpback chub is endemic to the Colorado River Basin and is part of a <br />native fish fauna traced to the Miocene epoch in fossil records (Miller 1958 <br />Minckley et al. 1986). Humpback chub remains have been dated to about 4000 <br />B.C., but the fish was not described as a species until the 1940's (Miller <br />1946), presumably because of its restricted distribution in remote white water <br />canyons (USFWS 1990b). Because of this, its original distribution is not <br />known. <br /> <br />Until the 1950's, the humpback chub was known only from Grand Canyon. During <br />surveys in the 1950's and 1960's humpback chub were found in the upper Green <br />River including specimens from Echo Park, Island Park, and Swallow Canyon <br />(Smith 1960, Vanicek et al. 1970). Individuals were also reported from the <br />lower Yampa River (Holden and Stalnaker 1975b), the White River in Utah <br />(Sigler and Miller 1963), Desolation Canyon of the Green River (Holden and <br />Stalnaker 1970) and the Colorado River near Moab (Sigler and Mille~ 1963). <br /> <br />Today the largest populations of this species occur in the Little Colorado and <br />Colorado Rivers in the Grand Canyon, and in the Black Rocks area of the <br />Colorado River. Other populations have been reported in Westwater and Debeque <br />Canyons of the Colorado River, Desolation and Gray Canyons of the Green River, <br />Yampa and Whirlpool Canyons in Dinosaur National Monument (USFWS 1990b). One <br />indivldual was recently captured in the Gunnison River (Burdick 1995). <br /> <br />Little is known about the specific spawning requirements of the humpback chub. <br />