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Table 2.-Dates when YOY Colorado squawfish monitoring occurred and average of mean-daily river flow (cfs) during the sampling period at USGS gaging stations nearest to the four ISMP sampling reaches. Colorado River Green River Reach 1° Reach 2 Reach 3 Reach 4 Sample Mean Sample Mean Sample Mean Sample Mean Yeaz Dates Flow Dates Flow Dates Flow Dates Flow 86 10/3-10/6 8,718 10/1-10/2 7,195 9/29-10/3 4,386 9/29-10/3 3,502 87 9/24-9/27 4,060 9/23-9/24 3,920 9/21-9/23 2,517 9/29-10/2 2,140 88 9/28-10/2 3,428 9/20-9/21 4,000 9/24-9/28 2,046 9/28-10/4 1,264 89 9/24-9/27 3,105 9/19-9/20 2,740 9/20-9/23 1,573 9/27-9/29 1,447 90 9/17-9/20 3,238 9/27-9/28 2,910 9/17-9/20, 1,530 9/24-9/26 1,433 10/15-10/16 91 9/16-9/19 5,030 9/19-9/20 4,995 9/16-9/19 2,660 9/19-9/20, 1,853 9/23,9/26 92 9/21-9/29 3,634 9/23-9/25 3,533 9/21-9/24 1,773 9/22-10/7 1,523 °Reach 1 =Colorado River at Cisco, Utah; Reach 2 =Colorado River at Colorado-Utah state line; Reach 3 =Green River at Green River, Utah; Reach 4 =Green River at Jensen, Utah. temperatures were typically warmer in the lower reaches of both rivers than in the upper reaches. Although YOY Colorado squawfish spend most of their time in backwaters which usually get warmer than the main channel during the day, main channel temperatures probably give a reasonable approximation of temperatures the fish are exposed to, and allow for comparisons among reaches and years. Distribution and Abundance Gmean CPE for YOY Colorado squawfish was usually higher in Reach 3 of the lower Green River than in the other three reaches (Figure 3; Table B-4). Gmean CPE in Reach 3 was exceeded by another reach on only three occasions: reaches 1 and 4 in 1992, and Reach 4 in 1991. Reach 3 had very high catch rates during the first 4 years of ISMP (1.8 to 5.6 CS/10 m~, but catch rates declined substantially in the last 3 years (0.2 to 0.5 CS/10 m2). The highest catch rate observed in Reach 4 was 1.2 CS/10 m2 in 1988. Gmean CPE in Reach 4 was between 0.1 and 0.8 during other years. The highest catch rate in both Green River reaches occurred in 1988. No other year came close to the high CPE observed in Reach 3 during 1988 (5.6 vs 2.8 CS/10 m2), but Reach 4 had two other years that came reasonably close to the high of 1988 (1.2 vs 0.8 and 0.82 CS/10 m~. The highest catch rates observed in the Colorado River occurred in 1986-Reach 1, 0.8 CS/10 m2 and Reach 2, 0.25 CS/10 m2-the first year of ISMP. Catch rates in both reaches declined steadily after 1986. Very few fish were caught from Reach 2, and it always had the lowest gmean CPE of any reach. Only one Colorado squawfish was caught from this reach in each of the last 5 years. 8