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<br />Executive Summary <br /> <br />However, this does not necessarily mean that humpback chub will be unable to <br />fmd opportunities once the cold-water restraints are eliminated. For example, it is <br />a well know fact that the humpback chub thrive in the wann water of the Little <br />Colorado River and that they compete very successfully against carp, catfish, and <br />other competitors in that wannwater system. Clear. summer-long, wanned <br />releases (about 13.50C) from Flaming Gorge Dam have also improved conditions <br />for native fish populations even though non-native fish are present in great <br />numbers. <br /> <br />. Predator Controls - Modeling studies underway by the Grand Canyon <br />Monitoring and Research Center suggest that carp and channel catfish populations <br />may need to be controlled by methods beyond the timing and duration of <br />temperature controls. Physical controls (harvesting) may be needed to reduce <br />predation on native fish in specific areas. Careful monitoring of these competitors <br />would be an important part of the proposed alternative. If physical controls are <br />needed, the Adaptive Management Work Group may reco=end to the Secretary <br />of the Interior actions that would be appropriate given the details of the <br />monitoring results and the problems that are identified. <br /> <br />. Rainbow Trout - Numerous experiences at other dams strongly suggest that the <br />proposed wannwater release of up to 150C would benefit the rainbow trout <br />fishery below Glen Canyon Dam by removing temperature stresses. The current <br />SOC (460F) releases are well below the 150C (590F) optimum for rainbow trout. <br />Reservoir modeling studies also suggest that nutrient and detritus releases from <br />the darn would increase, potentially improving the food base for trout in the Lees <br />Ferry reach of the river. <br /> <br />Adaptive Management - Adaptive management is an essential component of the <br />proposed alternative. Because of the complexity of the ecological interactions in the <br />Grand Canyon, no one (fixed) plan of operation could be expected to optimize the goals <br />of the proposed temperature control alternative. Modeling and predictions are of limited <br />usefulness when dealing with complex environmental systems. It is clear that <br />temperature release patterns (operations) will need to be adjusted and evolve as our <br />knowledge increases from each successive year of testing. Carefully monitored <br />experiments are necessary to assure that these adaptations help (not hann) the resources. <br />The testing and monitoring program would be developed by the Glen Canyon Technical <br />Work Group and Grand Canyon Monitoring and Research Center within the existing <br />adaptive management process. The Glen Canyon Adaptive Management Work Group <br />would then review this work and make reco=endations to the Secretary of the Interior <br />for implementation. <br /> <br />Monitoring - The temperature control alternative included in this assessment proposes <br />to avoid or mitigate the potential adverse impacts that have been identified in this <br />assessment. It also includes the Adaptive Management Program and Grand Canyon <br />Monitoring and Research Center to monitor and evaluate management options to avoid <br />unforseen impacts that may occur in the future. And finally, if monitoring shows that <br />wannwater releases do not to benefit endangered species, cold-water releases would be <br /> <br />IV <br />