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8 Post Larval. Aqe-O Colorado Squawfish Monitorinq Mean catch rates (fish / 100m2) of young-of-the year (YOY) Colorado squawfish from the lower Green River have varied significantly (F=5.14; df=9,378; p < 0.0001) over the past five years. Although the lower Green has consistently produced the greatest concentrations of YOY squawfish (Table 2), relative to the upper Green and the lower Colorado, the trend there has been downward since 1989 (Figure 6). Catch rates on the lower Colorado have hovered at relatively low levels (5 yr. avg = 7.03 /100m2) with the greatest abundance of YOY observed in 1986 (CPUE = 13.4) (Figure 7). In 1988, the catch rates on both the upper and lower Green River were significantly (p < 0.05) greater than the other four years. That year, over 600 YOY squawfish were caught in one secondary backwater in the lower Green, representing 20% of the total catch in that river reach. That particular backwater was sampled late in the day. While conducting these backwater surveys from year to year there appeared to be a tendency towards greater CPUEs in the late afternoon and evening hours, possibly due to elevated water temperatures. Table 2. Comparison of Mean Annual CPUE (Fish / 100 m2) of YOY Colorado squawfish from the Lower Green (RM 120 - 0), the Upper Green (RM 320 - 200), and the Lower Colorado (RM 110 -0). CPUE values represent sampling in 10 and 20 backwaters. CPOE OPPER LOWER LOWER YEAR GREEN GREEN COLORADO 1986 13.0 45.3 13.4 1987 6.4 28.9 7.8 1988 22.2 89.9 4.2 1989 1.5 35.1 3.4 1990 5.5 6.3 6.4 To alleviate this problem, the sampling protocol suggests that backwaters should not be sampled until they have warmed at least 20C more than the main channel, if possible. I" I I I I I I I I I I I , I I I I I I