Tuesday, May 19, 2009 - 9:00 AM
113

Diets of a fish assemblage in the Grand Canyon, Colorado River: Assessing potential interactions between native and non-native species

Kevin Donner1, Sarah E. Zahn2, Colden V. Baxter1, Emma J. Rosi-Marshall3, Dustin Kincaid2, Theodore A. Kennedy4, Wyatt F. Cross5, Michael D. Yard4, and Robert O. Hall Jr.6. (1) Stream Ecology Center, Department of Biological Sciences, Idaho State University, Pocatello, ID 83209-8007, (2) Department of Biology, Loyola University Chicago, 1050 W. Sheridan Rd, Quinlan 419-Dept of Biology, Chicago, IL 60626, (3) Biology, Loyola University Chicago, 1050 W. Sheridan Rd, Chicago, IL 60626, (4) USGS Grand Canyon Monitoring and Research Center, 2255 N. Gemini Dr., Flagstaff, AZ 86001, (5) Department of Ecology, Montana State University, Bozeman, MT 59717, (6) Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071

Native fishes of the Colorado River are imperiled due, in part, to interactions with non-native fishes, and competition with non-natives is likely a key mechanism driving reductions in native species. To evaluate the potential for such exploitative competition, we quantified diets and dietary overlap for the assemblage of fishes in a segment of the Colorado River in Grand Canyon.  During summer 2008, we collected diet contents from native humpback chub, flannelmouth sucker, bluehead sucker, and speckled dace, as well as non-native rainbow trout, carp, fathead minnow, and yellow bullhead. We identified diet items (invertebrates to family and other resources to coarse categories, e.g., algae, terrestrial plant material) and quantified prey types.  Substantial dietary overlap occurred between native and non-native fishes.  For instance, carp and flannelmouth suckers overlapped more than did the native suckers.  Strength of overlap varied with life history stage: e.g., suckers and fathead minnows had large overlap as juveniles, but little as adults.  Dietary overlap may be partially driven by the low diversity of food resources available in this regulated river.  Diet analyses from additional seasons and sites will allow more thorough assessment of interaction potential and description of resource use by the fish assemblage as a whole.


Web Page: large river fish, trophic basis of production, non-native species

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