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r ~ r <br />8 <br />in and around the Grand Valley, provide the best indication of use of the <br />15-mile reach above the confluence of the Gunnison River at one time or <br />another during the field season. Movement of these fish during a field season <br />was generally limited to 25-30 miles. <br />During 1986, the Fishery Project radio-telemetered three adult Colorado <br />squawfish collected from the 15-mile reach above the Gunnison River in June <br />(Kaeding and Osmundson 1987). The fish exhibited a diversity of localized <br />movement but spent a major part of the next 6 months in the reach upstream of <br />the Gunnison River. Two remained in the reach throughout the estimated <br />spawning period. <br />Spawning Activity <br />A suspected prespawning aggregation of adult Colorado squawfish was observed <br />by Fishery Project personnel at river mile 178.3 in the 15-mile reach above <br />the Gunnison River confluence in mid-July 1982. In the first observation, <br />three radio-tagged fish were tracked to one riverine pool area, and nine <br />adults at or near spawning condition were handled after limited net sampling <br />efforts. The aggregation occurred a few days after mean daily water <br />temperature had reached 20 °C and during a time when runoff flows were <br />dropping off sharply. A second aggregation was noted at river mile 175.3, <br />12 days after the initial observation. Drifting trammel nets through an area <br />occupied by two fish equipped with transmitters yielded an additional male <br />Colorado squawfish in spawning condition. During this same time period, an <br />adult female was captured near river mile 175 that weighed nearly 1 pound more <br />than when previously captured a month earlier, suggesting the development of <br />spawning (gravid) condition, <br />Larval Occurrence <br />Fishery Project studies included the routine sampling of the larval-fish <br />community both within and downstream of the 15-mile reach. During 5 years <br />of investigation, 46 larval squawfish were collected with fine-mesh hand <br />nets from two 15-mile reaches of the Colorado River immediately upstream <br />and downstream of its confluence with the Gunnison River. Although the <br />sampling effort was similar in the two river reaches, 96 percent of the <br />larval captures occurred immediately below the Gunnison River confluence <br />(river miles 162-164). Only two (4 percent) of the larvae were collected from <br />the upstream reach. These observations may indicate that most fish were <br />spawned in the downstream reach or that the larvae were spawned in the <br />upstream reach and drifted downstream to the area where most of the captures <br />were recorded. <br />Postlarval Young-of-Year Occurrence <br />No postlarval young-of-year Colorado squawfish greater than 25 mm total <br />length were collected from above the Gunnison River confluence in a total <br />of 57 samples collected in the fall of 1982-1986. However, a total of <br />62 Colorado squawfish were collected in the 15-mile reach below the confluence <br />of the Gunnison River (54 samples). The 1982-1984 catch rate of young-of-year <br />