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Abundance estimates for recruit-sized fish during 2000 to 2003 sampling in the Green River Basin averaged 8.9 % (4.7 to 13.3 %) of the estimated abundance of adult Colorado pikeminnow; recruitment rates may not be sufficient to offset mortality rates of adults. This suggested that apparent declines in abundance of adult Colorado pikeminnow in the Green River Basin in 2000 to 2003 were caused, in part, by lower recruitment rates. Reduced abundance of recruit-sized Colorado pikeminnow noted during this study may be due to weak year-classes of age-0 Colorado pikeminnow produced in the past several years in nursery areas of the middle and lower Green River. Average survival rate estimated for the average-size Colorado pikeminnow from 2000 to 2003 interval was 0.65 (95% Cl 0.586 to 0.708). Few captures and recaptures were made for fish > 800-mm TL, which resulted in very low apparent survival rates for those fish. The average survival rate for adult Colorado pikeminnow from 2000-2003 was lower than the 0.82 (95% Cl, 0.709 to 0.89) rate estimated for Colorado pikeminnow from Interagency Standardized Monitoring Program (ISMP) data collected from 1991 to 1999. This suggested that apparent declines in abundance of adult Colorado pikeminnow in 2000 to 2003 were caused, in part, by lower survival rates in those drought years. There was no support for the hypothesis that reduced survival of adult Colorado pikeminnow was due to sampling mortality. Apparent reductions in abundance of adult and recruit-sized Colorado pikeminnow in the Green River Basin may be due to low, drought-related base flows that began about the same time this investigation began. Flows were particularly low in the Yampa and White rivers. The precise mechanism for the apparent correlation between reduction in Colorado pikeminnow abundance and low flows is unknown. Reduced habitat area may have also increased potential 4