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Highest average catch rates of adult Colorado squawfish were obtained from the upper Green River (Strata G, E, F), and ranged from 0.62 to 1.1 fish per hour. Combined adult catch rates for the Green and lower Duchesne rivers averaged 0.53 fish per hour. Juvenile Colorado squawfish were most abundant in the lower Green River (Stratum A a 0.74 fish per hour and Stratum B 0.18 fish per hour); juvenile catch rates for all Green River strata averaged 0.17 fish per hour. Juvenile Colorado squawfish were not collected in the lower Duchesne River. The UCRBCC criterion for adult Colorado squawfish "high concentration" areas is a river reach where the electrofishing catch rates exceed 0.70 fish per hour, and an adult "concentration" area is a reach where catch rates exceed 0.30 fish per hour. A juvenile Colorado squawfish "high concentration" area would be a river reach where juvenile electrofishing catch rates exceed 0.3 fish per hour and a "concentration" area where the catch rates exceed 0.1 fish per hour. The above UCRBCC criteria do not specify the method of catch rate computation, and Table 3 shows that different catch rates result from the two methods used. Total catch indicates Strata B through G qualify as adult concentration areas, Stratum E as a high concentration area, and Strata A and B as juvenile high concentration areas (UCRBCC criteria). Data from other locations are near the minimum values for concentration and high concentration areas as well. Statistical tests using average catch rates indicated that the adult catch rate in Stratum A is not significantly different from those in Strata B, C, D and F (Student's T; p > 0.2). Thus, Stratum A cannot be eliminated from consideration as a concentration area. Average juvenile Colorado squawfish catch rates were significantly higher fvr Strata A and B than for Strata D, E 25