Tuesday, June 5, 2007 - 9:30 AM
120

A brief history of the Grand Canyon: developing an ecosystem perspective for conservation of native fishes in the Colorado River

Theodore A. Kennedy1, Emma J. Rosi-Marshall2, Robert O. Hall Jr.3, Colden V. Baxter4, Wyatt F. Cross3, Holly A. Wellard2, and Michael D. Yard4. (1) USGS Grand Canyon Monitoring and Research Center, Flagstaff, AZ 86001, (2) Biology, Loyola University Chicago, Chicago, IL 60626, (3) Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, (4) Stream Ecology Center, Department of Biological Sciences, Idaho State University, PO Box 8007, Pocatello, ID 83209-8007

Closing Glen Canyon Dam in 1963 dramatically altered the physical template of the Colorado River. Introductions of non-native invertebrates and fishes have been extensive and macroinvertebrates are now limited to low-diversity non-native assemblages. Native fish populations have also declined; four species of native fish have been locally extirpated and one of the four remaining species, humpback chub (Gila cypha), is federally endangered.  In 1996, adaptive management strategies were initiated to mitigate these unintended consequences of the dam.  Some strategies that have been employed include removing non-native trout from important chub habitat, implementing two experimental floods, and reducing daily flow fluctuations associated with hydropower generation.  Although extensive research on population dynamics of chub has been conducted over the past 15 years, measurements of ecosystem-scale processes have been limited. We are currently quantifying carbon budgets and quantitative food webs at 6 sites within the 385-km reach downstream of Glen Canyon Dam.  A thorough understanding of food webs and ecosystem-level processes will help address to what degree food resources limit production of the humpback chub. Our research goals on carbon cycling and energy flow will identify strategic dam operations that enhance food resources critical to native fish populations.

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