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. DRAfT . behavior. During periods of low flow in year 1, more backwater habi tat became available and correspondingly more squawfish were found in backwaters indicating that the foraging squawfish were attracted to these areas by concentrations of small fishes. Use of ice-covered backwaters during both years indicates that the fish were both foraging and resting in this habitat. 6.2.2 Razorback Sucker . During the first year of the investigation, 8 radiotagged razorback suckers were observed in only two habitat types; runs and eddies. The fish spent approximately 64 and 31% of the time in these habitats, respectively (Figure 17A) . . During year 2, the 10 razorbacks observed during ice-free conditions used runs, eddies and slackwaters approximately 48, 30, and 22% of the time, respectively (Figure 17B). Use of the term slackwater is explained in the section above for Colorado squawfish. These fish used runs (89%) almost exclusively during iced conditions in year 2, although some habitats were probably slackwaters but could not be distinguished because of the ice cover (Figure 17C). . Like the Colorado squawfish, razorback suckers used winter habitats that were characteristically of moderate depth and low velocity. Their selection for these habitats also seemed to be driven by low near-bottom velocity. However, unlike squawfish, razorbacks did not appear to use ice as a cover element. Their use of depth, velocity and substrate is explained in detail in the section on HSI CUrve Development. . 6. 3 RES~SE OF HABITATS AND RADIOTAGGED FISH TO TEST FI..CMS . Flows requested by BIO;WEST and provided by BOR proved very valuable in observing the effect of sudden and dramatic changes in flow stage on the habitat and the fish. This information may be the most important in assessing flow needs by the fish. These test flows were provided three times during the study and will be described more fully in later drafts of this report. For now, a description is provided of the test flows observed on January 7, 1988 at Rainbow Park. . Test flows were released from Flaming Gorge on January 6, 1988, and observed in Rainbow Park on the morning of January 7, 1988. Flows were raised from 800 cfs to 4000 cfs starting at 7:00 am and maintained until 8:00 pm on January 6. A realized low flow of 1500 cfs was predicted to reach Rainbow Park at 9:00 am and steadily increase to a high of 3900 cfs at 5:00 pm. Two crews monitored a total of three fish (two Colorado squawfish, OR-3235, OR- 3236; and one razorback sucker, OR-3234) during the 10-hour daytime observation period of 8:00 am to 6:00 pm, recording fish movement and relative water level. . . Inclement weather and very hazardous riverine ice conditions impeded the crews from contacting the fish very early on January 7. Nevertheless, a semi- permanent staff gauge was established near the fish and monitored starting at 8:56 am (a hole had to be drilled through the ice and water level monitored in the hole). Relative water level readings were recorded periodically until 4:50 pm. A minimum relative water level (RWL) of 422 rom was recorded on the first 34 .