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. DRAFT . times during the 1987-88 winter, twice within 0.5 mile of a site used the previous winter. Three of the razorback suckers (GR-3266, GR-6116 and GR- 6117) were located either in the same location or within 0.2 mile of sites occupied the previous winter, while razorback sucker GR-2417 was found in two sites and within 0.1 mile of a third used by the fish the previous winter. Razorback GR-6116 was located by FWS on May 12, 1988, subsequent to field work by BIO;WEST. . 6.1.4 Movement To Changing Conditions As a result of these analyses, three variables were identified that appeared to cause local movement by these fish; (1) fluctuating water levels, (2) presence of moving ice masses, and (3) unidentified behavior modes such as feeding. . During observation periods of several hours, some of the radiotagged fish initiated local movement during large decreases or increases in water level. In the presence of ice, movement often occurred in response to changes in water level and large ice masses; increasing water levels dislodged and transported large masses of ice through the habitat occupied by the fish, apparently forcing the fish to move frequently to avoid the ice pieces. Such activities as feeding remain unidentifiable because of water turbidity. . In an effort to isolate the mechanism which caused the fish to move, local movement was assessed for fish during changing water levels as well as for fish under ice cover and in the absence of ice cover . 6.1.4.1 Movement In Response To Changing Water Levels . Observations during 24-hour monitoring indicate that fluctuating water levels were responsible for much of the diel movement. Most major movements by both species of fish coincided with either rising or falling river levels. River fluctuations were erratic and unpredictable due to variable discharges from Flaming Gorge Dam and the time lag associated with the changes in flow to reach any given location downstream. This confounds interpreting the influence of other physical factors that may be responsible for activity or movements by the fish, such as time of day. . A small amount of local movement is believed to be normal. However, movement by both species during significant changes in river flow is perceived to be in response to changes in habitat. This is best illustrated with sketches of selected ice-free river reaches in which one or more radiotagged fish were observed over a 24-hour period. Selected observations are presented in Figures 5 - 9 for each species from the upper, middle, and lower regions of the study area, through which vertical changes in water level decrease with distance from Flaming Gorge Dam. Each sketch is accompanied by a hydrogaph with the movements of the fish depicted in order to relate these to flow. . 6.1.4.1.1 Colorado Squawfish . A total of four radiotagged squawfish were selected to depict local movement in three regions of the Green River relative to Flaming Gorge Dam; one in the upper region near Echo Park at RM 343.8 (Figure 5), one in the middle region 29 .