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Maybell, and Yampa Canyon. The potential for smallmouth bass movement among reaches was shown by movements of up to 50 miles (80 km) in less than a year and up to 100 miles (161 km) after periods of more than a year. Documenting the rate of immigration into our study sites and improving our knowledge of movement dynamics in the Yampa River will require increased tagging effort in the Craig, South Beach, and Maybell reaches. Long-range movements of smallmouth bass throughout the Yampa River suggest that expanded and higher removal rates are needed river wide if we are to sustain removals in our study reaches. We observed biological and environmental differences between Little Yampa Canyon and Lily Park study sites that may provide insight into the interactions and population dynamics of smallmouth bass and native fish populations. For example, density of smallmouth bass ranged from 100 to 143 fish per mile (62-89 fish/km) at Little Yampa Canyon and from 247 to 393 fish per mile (153-244 fish/km) at Lily Park. Smallmouth bass larger than 250 mm comprised 11 % of the bass at Lily Park and 43% of the bass at Little Yampa Canyon. Smallmouth bass were extremely rare at both sites 23 years ago when native fishes were a dominant part of the fish community. Smallmouth bass numbers have increased from near zero to 51 % of the fish community from 1984 to 2007 at Little Yampa Canyon and from zero to 25% of the fish community at Lily Park during the same period. In 1983 and 1984, native fish comprised 91 % of the fish community at Lily Park and 67% of the fish community at Little Yampa Canyon. In 2007, native fish comprised no more than 8% of the fish community at Little Yampa Canyon and 56% of the fish community at Lily Park. Smallmouth bass are now the dominant predator in the middle Yampa River and their rise in abundance was concurrent with the decline of native fish in the Yampa River. Higher removal rates, both within the study area and at other study areas may be needed to adequately reduce the predatory threat of smallmouth bass in the Yampa River and to restore the native fish community. vii