2013-03-06_REVISION - C1992081 (6)

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f ;P, .I 13 captures of ripe specimens, both males and females, have been recorded (Valdez et al. 1982; McAda and Wydoski 1980; Tyus 1987; Osmundson and Kaeding 1989; Tyus and Karp 1989; Tyus and Karp 1990; Osmundson and Kaeding 1991; Platania 1990) in the Yampa, Green, Colorado, and San Juan Rivers. Sexually mature razorback suckers are generally collected on the ascending limb of the hydrograph from mid -April through June and are associated with coarse gravel substrates (depending on the specific location). Outside of the spawning season, adult razorback suckers occupy a variety of shoreline and main channel habitats including slow runs, shallow to deep pools, backwaters, eddies, and other relatively slow velocity areas associated with sand substrates (Tyus 1987; Tyus and Karp 1989; Osmundson and Kaeding 1989; Valdez and Masslich 1989; Osmundson and Kaeding 1991; Tyus and Karp 1990). Habitat requirements of young and juvenile razorback suckers in the wild are largely unknown, particularly in native riverine environments. Life stages, other than adults, have not been collected anywhere in the Upper Basin in recent times. The last confirmed documentation of a razorback sucker juvenile in the Upper Basin was a capture in the Colorado River near Moab, Utah (Taba et al. 1965, reported in Bestgen 1990). Razorback Sucker Activity in the 15 -mi]e Reach Osmundson and Kaeding (1989) found that 76 percent of the razorback suckers captured between 1979 and 1985 were captured in the Grand Valley area. Results of surveys conducted during May and June of 1986 -1988 indicate that areas within the 15 -mile reach may be concentration points for the razorback sucker during spring runoff. Male and female razorback suckers in spawning condition have been found in the 15 -mile reach, although no larvae or juveniles have been found. Although data is limited, Osmundson and Kaeding (1989) think razorback suckers may move into the 15 -mile reach to spawn in the spring, and some individuals may move into lower reaches during the remainder of the year. The current range of the razorback sucker in the Colorado River extends upstream to Rifle, Colorado. Most razorback suckers captured in the Grand Valley area have been located in flooded gravel -pit ponds adjacent to the river. However, Osmundson and Kaeding (1989) documented razorback sucker movement in various river habitats in the Grand Valley area. They documented razorback suckers at river mile 183.6 and at several other locations downstream. Humpback Chub Humpback chub generally do not make migrational movements in the upper Colorado River and tend to reside throughout the year within a limited reach of river. Humpback chub are found inhabiting narrow, deep canyon areas and are relatively restricted in distribution. They seldom leave their canyon