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<br />Environmenral Biology of Fishes 40: 227-239,1994.
<br />O 1994 Kluwer Academic Publishers. Printed in the Netherlands.
<br />x'151
<br />Fish species composition before and after construction of a main stem
<br />reservoir on the White River, Colorado
<br />Patrick J. Martinez, Thomas E. Chart2A, Melissa A. TrammellZ.', John G. Wultschleger2,1 & Eric E Bergersen'
<br />'Colorado Division of Wildlife, Wildlife Research Center, 317 West Prospect, Fort Collins, CO 80526, U.S.A.
<br />z Colorado Cooperative Fish and Wildlife Research Unit3, 201 Wagar Building, Colorado State University, Fort
<br />Collins, CO 80523, U.S.A.
<br />s Cooperators are the US Fish and Wildlife Service, the Colorado Division of Wildlife, and Colorado State
<br />University
<br />' Current address: Utah Division of Wildlife Resources, Moab Native Fishes Field Station, P. O. Box 388, Moab,
<br />UT 84532, U.S.A.
<br />Current address: Utah Division of Wildlife Resources, Northern Regional Office. 515 East 5300 South, Ogden
<br />UT 84405, U.S.A.
<br />Received 18.6.1993 Accepted 8.12.1993
<br />Key words: Ichthyofauna, Colorado River Basin, Impoundment, Nonnative fish, Habitat changes, Distrubu-
<br />tion, Ptychocheilus lucius, Gila, Catostomus, Rhinichthys, Cyprinidae, Centrarchidae, Ictaluridae, Salmoni-
<br />dae
<br />Synopsis
<br />The completion in the fall of 1984 of Taylor Draw Dam on the White River, Colorado, formed Kenney Reser-
<br />voir - thus impounding the last significant free-flowing tributary in the Upper Colorado River Basin. Fishes
<br />were sampled above and below the dam axis prior to closure of the dam and in the reservoir and river down-
<br />stream following impoundment. While immediate effects of the dam to the ichthvofauna included blockage of
<br />upstream migration to 80 km of documented range for endangered Colorado squawfish, the reservoir also
<br />proved to have profound delayed effects on the river's species composition. Pre-impoundment investigatiolis
<br />in 1983-1984 showed strong domination by native species above. within, and below the reservoir basin. By
<br />1989-1990, non-native species comprised roughly 90% of the fishes collected in the reservoir and 80% of the
<br />fishes collected in the river below the dam. Initially, fathead minnow, whose numbers quickly increased in the
<br />new reservoir. dominated all post-impoundment collections, but red shiner became the most abundant fish
<br />collected in the river below the dam by 1989-1990. While agency stocking programs for the reservoir sought to
<br />emphasize a sport fishery for salmonids, primarily rainbow trout, local enthusiasm for warmwater sport fishes
<br />resulted in illicit transfers of these species from nearby impoundments. Several species, formerly rare or
<br />unreported in the White River in Colorado, including white sucker, northern pike, green sunfish, bluegill,
<br />largemouth bass and black crappie, were present in the river following impoundment. Our investigation in-
<br />dicates smaller-scale, main-stem impoundments that do not radically alter hydrologic or thermal regimes can
<br />still have a profound influence on native ichthyofauna by facilitating establishment and proliferation of non-
<br />native species.
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