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. . ~ 10 specific impacts that would result to this reach of the Colorado River from such a reduction is undetermined at this time, although the depletion of water will contribute to a cumulative loss of habitat below the Gunnison. It is assumed that the flows contributed by the Gunnison River and other tributaries will prevent a condition as critical as that found in the IS-mile reach above the Gunnison. In addition, specific flow windows have not yet been established for occupied habitat areas in the reach below the Gunnison River, preventing an effective analysis of pre-project and post-project impacts. Therefore, for the purposes of this opinion, analysis of the water depletion impacts resulting from the Ruedi water sale will concentrate on the 15-mile reach above the confluence of the Gunnison River. Documented Colorado Squawfish Activity in the Colorado River between Palisade and the Confluence with the Gunnison River Migration Radiotelemetry studies show upstream and downstream movement of adult Colorado squawfishin the main stem Colorado River. The most dramatic movement was exhibited by a fish implanted with a radio transmitter at Gypsum Canyon in upper lake Powell on April 5, 1982. The fish was contacted next in the lower Cataract Canyon area on July 9. The next contact point was above the Blackrocks area of Ruby Canyon, some 160 miles upstream. The movement was accomplished in 41 days, and was thought to be related to spawning. At the end of September 1982, this fish was located between Palisade and the Gunnison confluence near Clifton, Colorado, nearly 200 river miles from its farthest-documented downstream location. Other- radio-tagged fish have not displayed such dramatic migratory behavior. Radiotelemetry studies conducted by Colorado River Fishery Project (CRFP) from 1982 to 1985, which focused on upstream reaches of the Colorado River in and around the Grand Valley, provide the best indicator of use of the IS-mile reach by Colorado squawfish. Of the 34 radio-tagged fish that were initially captured upstream from Blackrocks, 15 (44 percent) occupied the IS-mile reach above the confluence of the Gunnison River at one time or another during the field season. Movement of these fish during a field season was generally limited to 25-30 miles. Spawning Activity A suspected prespawning aggregation of adult ColoradO squawfish was observed by FWS CRFP personnel in the IS-mile reach at RM 178.3 near Clifton, Colorado, in mid-July, 1982. In the first observation, three radio-tagged fish were traced to the same riverine pool area, and nine adults at or near spawning condition were handled after limited net sampling efforts. The aggregation occurred a few days after both maximum and mean daily water temperature had reached 20 degrees C and during a time when runoff flows were dropping off sharply. A second aggregation was noted at RM 175.3, 12 days after the initial observation. Drifting trammel nets around two fish equipped with transmitters yielded an additional male Colorado squawfish in spawning condition.