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Elizabeth Estill, Regional Forester 9 <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 <br />from 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 Younq -of -Year Occurrence <br />No postlarval young -of -year Colorado squawfish greater than 25 mm total length <br />were collected from above the Gunnison River confluence in a total of <br />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 />Colorado squawfish in the 10 -mile reach immediately downstream of the <br />confluence of the Gunnison River (river miles 160 -170) warranted <br />classification of this reach as a "Young -of -Year Nursery Area" by the Basin <br />Biology Subcommittee (U.S. Fish and Wildlife Service 1984). <br />Nonspawning Adult Occurrence <br />Although the sampling effort was similar between the reaches upstream and <br />downstream of the Gunnison River, over 60 percent of the adult -size Colorado <br />squawfish collected during spring surveys by the Fishery Project (Miller <br />et al. 1982; Kaeding and Osmundson 1987) came from the upstream 15 -mile reach. <br />Kaeding and Osmundson (1987) reported that adult Colorado squawfish catch <br />rates in the upstream 15 -mile reach were twice as high as those in the <br />adjacent downstream river reach. Adults were most abundant in a 0.6 -mile <br />segment (river miles 174.4- 175.0) of the 15 -mile reach during high water, <br />particularly in two gravel -pit ponds that were accessible during high flows. <br />These fish may have moved into these ponds to feed and rest, or they may have <br />been attracted to the warm, productive environments that the ponds provided <br />