A creel survey was conducted at the Keystone stilling basin to determine differences in pressure, harvest, and species composition between hydropower generation discharge and non-discharge periods. Pressure during discharge was 1.7 times greater than during non-discharge. Total harvest during generation discharge was 1.8 times that of non-discharge and was dominated by striped bass. Striped bass harvest rate was 3 times greater during discharge. During non-discharge, white bass, channel catfish, and blue catfish became important species in the harvest. No patterns of white or striped bass harvest were observed within generation discharge or non-discharge periods. When generation time is reduced and discharge volume increased, potential losses of fishing opportunity in eastern Oklahoma tailwaters can be economically substantial. Mitigation measures which prevent these losses, without withholding benefits of increased hydropower, should be considered.