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<br />JI <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />The decline in channel catfish biomass. observed at Lily Park from 2000 to 2003, <br />may have occurred regardless of the removal project. Several non-target species also <br />experienced a large drop in density and biomass during the study period. The low summer <br />flows in 2000 were suspected of interrupting migrating channel catfish at Cross Mountain <br />Canyon. This would have resulted in an inflated channel catfish population in 2000 <br />compared to a typical year. <br /> <br />Fuller (2003) reported a decline in mean length of channel catfish from 2000 to 2003 <br />in Dinosaur Canyon and attribut"d reduced mean size in the canyon to the catfish removal <br />project. Declin~s in mean length of channel catfish were also observed at Lily Park from <br />2000 to 2003, The reduced mean length at Lily Park was due to a very high increase in fish <br />between 20 and 30 em compared to prior years, indicating much improved recruitment of <br />Age-I and Age-2 fish at Lily Park in 2003. Changes in age composition between years may <br />have been related to the Spring and Summer hydrograph, Wanner water temperatures in <br />200 I and 2002 could have altered the timing and location of channel catfish spawning. In <br />years with warmer water temperatures spawning would likely be located further upstream <br />making Lily Park more accessible to younger and smaller channel catfish. <br /> <br />Northern pike is another predator that has been suspected of having significant <br />impacts to the native fish community, The impacts of northern pike were most obvious <br />during the baseline years prior to the drought conditions. Abundance of northern pike <br />appeared to decline during the drought years, Pike could recover quickly, however, given a <br />return to improved prey and habitat availability. <br /> <br />Maintenance of the peak flow hydrograph in the Yampa River was identified as a <br />high priority in regard to recovery of endangered species (Modde and Smith 1995). Peak <br />flows appeared to have had little overall negative impacts on nonnative fish abundance <br />during the study period, Currently, the Yampa River has a depopulated native tish <br />community, Nonnative fish were highest in 2003, a year with an above average peak flow of <br />12,900 m3/s, Also, peak flows were near normal during the study period, except in 2002, <br />Small mouth bass numbers increased in years of normal (median) runoff flows. Also, high- <br />peak flows may have assisted in their rapid expansion by flushing young fish to downstream <br />habitats, <br /> <br />COLORADO RIVER, 15-MILE REACH <br /> <br />Species composition data collected in the IS-Mile Reach between 1999 and 200 I <br />were highly consistent with U,S. Fish and Wildlife surveys made in 1994 and 1995 by <br />Osmundson (1999). <br /> <br />The Colorado River experienced one year with poor flow conditions in 2002, unlike <br />the Yampa River which had three consecutive poor base flow years. Upstream of the roller <br />dam in Debeque Canyon, the Colorado River did not experience severe drought flows <br />because of water deliveries to the Highline Canal. Since flows were nonnal above the roller <br />dam, the fish community in that reach should not have been negatively impacted by altered <br />habitat conditions. Excess or displaced fish from above the roller dam could migrate <br /> <br />37 <br />