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SUBADULT-ADULT COLORADO SQUAWFISH Unlike YOY Colorado squawfish monitoring, subadult-adult monitoring was not a direct continuation of studies done by earlier investigators. However, spring electrofishing of some form was done regulazly in the 1970's and 1980's-the Colorado Division of Wildlife had a formal monitoring program in rivers within Colorado (Wick et al. 1981, 1985a, 1985b) and the Service regulazly sampled in different parts of the basin as pazt of their studies (Tyus et al. 1982, 1987; Valdez et al. 1982; Archer et al. 1985). Some of this sampling evolved into a spring monitoring program in the Green River when the same azeas were electrofished every year at about the same time (Tyus et al. 1987). Considerable sampling was also done in the Colorado River every year, but sampling times and azeas vazied from yeaz to yeaz. More recent sampling in parts of the Colorado River not sampled by ISMP became more consistent from yeaz to yeaz and complements the monitoring program (Osmundson and Kaeding 1989). The Biological Subcommittee (1984) used the data mentioned above to delineate reaches where most subadult or adult Colorado squawfish had been captured during the earlier studies. Some of the reaches described in the Sensitive Areas Document (Biological Subcommittee 1984) were modified slightly to accommodate logistic considerations and make sampling more efficient. The azeas sampled for ISMP were not the only reaches occupied by Colorado squawfish, nor were they necessarily the most important reaches, but ISMP participants felt that these reaches composed sufficient adult habitat within the upper basin that they could be used to monitor trends in the population. Sampling Reaches The subadult-adult Colorado squawfish monitoring program samples 186 miles of four rivers in the upper Colorado River Basin-the Green (five reaches, 77 miles), Colorado (three reaches, 54 miles), White (two reaches, 30 miles) and Yampa (three reaches, 25 miles) rivers (Figure 9). These reaches compose about 20 to 30Ro of occupied habitat within each of the four rivers. The following information briefly describes the 13 sampling reaches. Green River Reach 1-A 7-mile section located in Island and Rainbow parks within Dinosaur National Monument. The sample reach is between Whirlpool and Split Mountain Canyons. Gradient is high (mean, 10 ft/mi) with an abundance of cobble and rubble substrate in the Island Pazk portion, but gradient is reduced (2 ft/mi) and substrates aze smaller in the lower Rainbow Park segment. Islands and side channels aze common in this section. No significant tributaries enter the Green River in Reach 1. Reach 2-This section begins at the Dinosaur National Monument bridge neaz Chew Ranch and continues downstream 18 miles to a point about 0.5 miles downstream from the confluence of Ashley Creek. The upper 8 miles of this reach aze higher gradient (5.5 ft/mi) with cobble-rubble substrate and the lower 10 miles aze low gradient (1.8 ft/mi) with sand substrate. Two significant tributazies- Brush Creek and Ashley Creek-enter the Green River within this reach. Reach 3-Reach 3, the lowermost Green River reach within the Uintah Basin, begins at the upper end of Leota Bottom within Ouray National Wildlife Refuge and continues downstream 17 miles to an island about 1 mile below the mouth of the White River. The entire reach is low gradient 26