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Hypothesis 1: Reproductive success of Colorado squawfish in the Colorado River <br />is greatest during years with maximum-annual discharges of 30,000 to <br />40,000 cfs (measured at the Cisco stream gage). Reproductive success is <br />reduced in years with higher or lower peak discharges. <br />Hypothesis 2: High spring flows reduce the survival of age-0 Colorado <br />squawfish by reducing the growing season and thus the size of the fish <br />entering their first winter. <br />Hypothesis 3: High spring flows reduce non-native fish populations. <br />The Interagency Standardized Monitoring Program samples for age-fl <br />Colorado squawfish every fall. The mean catch-per-unit-effort of these <br />samples measures the variation in abundance of this size class among years and <br />is a useful indicator of the annual reproductive success of the species. As <br />shown in this report, the abundance of age-0 Colorado squawfish in the <br />Colorado River is related to the maximum-annual streamflow that occurred the <br />previous spring. Increased runoff in the Gunnison River (and thus the <br />Colorado River) and the continuation of the monitoring program will be an <br />effective test of this relationship. Survival of the young Colorado squawfish <br />is very important in determining the total number of fish that recruit to the <br />adult population. Investigations should not only consider what environmental <br />conditions result in the greatest number of young fish, but what conditions <br />result in the highest survival of the fish that are produced. Many factors <br />(i.e. length of fish at the end of their first growing season or winter <br />conditions) can influence the survival of the small fish. Studies to evaluate <br />the over-winter survival of these fish have been conducted for the last three <br />34 <br />