ABSTRACT
Introduced trout have become increasingly important to the Colorado River below Glen Canyon Dam, Arizona. The presence of a multi-million dollar rainbow trout (Oncorhynchus mykiss) fishery in the Lee’s Ferry tailwater influences much of dam management activity. Since the closure of Glen Canyon Dam, different flow regimes have altered the composition of the trout population. Current flows are designed to enhance the fishery to best suit the desires of anglers. Trout are found in decreasing numbers all the way down to Lake Mead, but little is known about the ecology of trout outside of the tailwater. The implementation of other management tactics such as the “trout removal program” centered at the mouth of the Little Colorado River, aims to reduce trout densities in critical habitat areas for Humpback Chub (Gila cypha). Contradicting management actions make it difficult to understand fisheries management objectives. With one of its many goals to harm exotic fish populations, the 1996 flood release failed to decrease trout numbers. Since 2003, the winter flow hydrograph out of Glen Canyon Dam has been altered completely with hopes of creating a healthier tailwater trout population composed of bigger fish. These fluctuating winter flows have proven somewhat successful in decreasing recruitment but the desired changes in the fishery have not been conclusive. Management in the interest of trout may detract from efforts to conserve and restore populations of native fishes. Future management goals will determine the fate of Colorado River trout.