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was an estimated 4,217 cfs compared with mean flows in 1988 of 2,445 cfs in July and 1,634 cfs in August). For introduced minnows, low flows are probably beneficial because these species may be more adapted to stable environments, such as those provided by unflooded backwaters. We concur with Valdez (1990), who suggested that high flows probably flush these fish from their otherwise protected micro- habitats and into the main channel, and that turbulent conditions and delayed warming of the river during years of high flow may interfere in some way with their ability to reproduce and recruit. Why correlations for a given species were not identical among reaches might be due to differ- ences in reach characteristics such as flow regime and channel morphology (gradient, substrate, degree of channelization, availability of refugia habitats, etc.). Difference in water temperatures between the 15-mile and 18-mile reaches was slight (Osmundson and Kaeding 1989), and probably would not account for differences in fish abundance. Abundance of ictalurid larvae and YOY was not correlated with peak flow. No larvae of channel catfish or black bullhead were detected during the four-year study, though YOY black bullhead were collected in both the 15- mile and 18-mile reaches. Channel catfish YOY were collected only from the 18-mile reach. Because channel catfish adults are numerous in the Grand Valley (Valdez et al. 1982), the rarity of young in samples may reflect their preference for habitat types other than those that we sampled rather than an actual scarcity in the river. Or, larval drift and later recoloni- zation by adults from downstream reaches might explain discrepancies in age-structure of the local population of this species. In either case,, our 24