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<br />Study 2: Winter habitat and flows for adult and young Colorado squawfish, and <br />adult razorback sucker. <br /> <br />Report 3- <br /> <br />Winter habitat study of endangered fish-Green River. Wintertime <br />movement and habitat of adult Colorado squawfish and razorback <br />suckers. (Valdez and Masslich 1989) <br /> <br />Ten radiotagged Colorado squawfish and eight razorback suckers <br />overwintered in specific areas of the Green River during the winters of 1986- <br />87 and 1987-88. These areas were generally less than about 5 km, but maximum <br />movement of Colorado squawfish ranged from 41.4 km downstream to 35.5 km <br />upstream, and maximum movement of razorback sucker ranged from 16.8 km <br />downstream to 11.7 km upstream. Colorado squawfish and razorback suckers <br />exhibited local diel movements in selected low velocity microhabitats, These <br />habitats were characterized by average water depth of 0.76 to 1.37 m and mean <br />water column velocity of 0 to 0.31 mps for Colorado squawfish, and 0.61 to <br />1.37 m and 0.03 to 0.335 mps for razorback sucker. Movements of Colorado <br />squawfish in eddies and backwaters (48,20 m/h) was greater than in slow runs <br />and slackwaters (21.71 m/h), suggesting foraging in the former and resting in <br />the latter. Greater local movement was exhibited by adult Colorado squawfish <br />and razorback suckers exposed to fluctuating river levels, and flow <br />fluctuation rates greater than 5 cm/h caused about 190 percent greater <br />movement in adult Colorado squawfish and 39 percent greater movement in adult <br />razorback suckers. This movement increased during periodic ice breakups. Fish <br />in the upper 88 km of their distribution in the Green River can be expected to <br />move more frequently than fish further downstream in order to remain in <br />suitable microhabitats. The effect of this energy expenditure on survival, <br />growth, and reproductive potential is unknown. (Authors abstract from Summary <br />of Findings) <br /> <br />Report 4- Winter habitat use of young Colorado squawfish. (Tyus, in litt.) <br /> <br />Shoreline habitats and general river conditions were studied during the <br />winters of 1987-88 and 1988-89. Weather conditions differed between the two <br />winters, but ice cover generally formed by mid-December. Few fish were <br />captured using baited minnow traps, but 5 young Colorado squawfish were <br />collected in one backwater in December 1987 and one hatchery-reared juvenile <br />razorback sucker was captured in 1988. Fluctuating flows in 1987-88 caused <br />shoreline scouring in the Jensen area by moving blocks of ice, and alternate <br />flooding and dewatering uf low.ljing areas at Ouray due to ice jams. Lower, <br />more stable flows in 1988-89 resulted in shallower backwaters but less <br />shoreline scouring. (Unpublished manuscript) <br /> <br />Study 3: Spring-early summer flow requirements of Colorado squawfish, <br />razorback sucker, and humpback chub. <br /> <br />9 <br />