A 12-year study of the smallmouth bass population, Micropterus dolomieui, in a pumped storage reservoir revealed an accelerated growth that was related to the abundance of gizzard shad, Dorosoma cepedianum. Prior to the gizzard shad introduction, the growth of smallmouth bass was generally poorer than that reported for the mid-Atlantic region. Large drawdowns (9 m per day, 15.6 m per week) may have increased the vulnerability of gizzard shad by concentrating both prey and predator. In the lower reservoir, where water levels fluctuated irregularly and much less (up to 1 m per day), smallmouth bass growth was not greatly improved following the introduction of gizzard shad.