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downstream during the 2003 runoff lfso, this would mask the impacts of poor habitat conditions in the IS-Mile Reach in 2002, The 2003 data did not suggest a fish community that had been stressed by a severe environmental event. In fact. the fish community data in 2003 was very similar to prior years, This indicates that one year of low flows did not have a significant negative impact on native fish. The data did suggest that nonnative fish were more resistant to drought conditions than native species, The species with the largest negative impact was bluehead sucker, which is a deep-riffle habitat species (Anderson and Stewart 2003). Deep-riffle habitat is lost at low flows making this species the most vulnerable to habitat loss during drought conditions, Adult flannelmouth sucker and roundtail chub density and biomass were stable in 2003, but a poor 2002 year-class indicated reduced reproductive success for these two species compared to baseline years, The species with the largest increase in the IS-Mile Reach in 2003 was carp followed by channel catfish and white sucker. The carp population had been a significant part of the community in the IS-Mile Reach for a long period. Adult carp habitat at flows near 1,000 cfs appeared to be restricted to shoreline areas with cover and backwaters, Suitable habitat for carp likely increased with lower flows since area of low velocity pools increase under these conditions (Anderson and Stewart 2003). Anderson and Stewart (2003) determined that backwater or nursery habitat availability increases with decreasing flows. This appears to suggest that lower flows, as observed in 2002, could be beneficial for recruitment of Age-O native fish. However, the biological data found this had not happened in either the IS-Mile Reach or the Yampa River. In the IS-Mile Reach habitat diversity was maximized at flows near 1,000 cfs (Anderson and Stewart 2003), Also in 2000 and 2001, years with base flows near lOOO cfs, Age-O and Age- l native fish were commonly collected. The fact that the adult population of native sucker and roundtail chub appeared to be at carrying capacity further suggested recruitment of juveniles had been sufficient in years with base flows over 800 cfs, These facts indicated that reducing flows to increase backwater habitat for nursery areas for native species would be counter-productive, Small mouth bass made their first noticeable appearance in 2003, This coincided with the first year of low flows for the IS-Mile Reach, It was observed in 2003 that there were much fewer Age-O and Age-I white sucker collected in backwater habitats compared to prior years. It was observed on the Yampa River low flow years coincided with increased abundance of centrarchid predators. Increased predation likely explained the reduced presence of Age-O and Age-l white sucker in 2003 in the IS-Mile Reach, An increase in channel catfish was observed in 2003 compared to earlier years, This could be within the range of sampling variation, but it also suggested habitat was improved in 2002 compared to years with the normal 900 cfs plus flows. It was noted that at Lily Park where there was a very large channel catfish population there were very few roundtail chub. 38 I I I I I I I I I I I I I I I 1 I I I