We studied fish populations in four lakes in southwestern Oklahoma before and after stocking striped bass (Morone saxatilis) X white bass (M. chrysops) hybrids to determine if the population structure changed as a result of predation by the hybrids. Two lakes were stocked with hybrid fmgerlings at 45 fish/ha in fall 1979 and again with fry at 120 fishlha in spring 1980. The other two lakes (the controls) were not stocked Although growth of hybrid fmgerlings was good, survival was poor. Mortality was greatest for fingerlings less than 150 mm in total length at the time of stocking. None of the fry stocked was recovered Based on the distribution of hybrids and their food, it appeared that they utilized primarily the limnetic zone and did not feed extensively on centrarchids. Changes in the "apparent" structure of populations of bluegill (Lepomis macrochirus) were not consistent and could not be attributed to predation by hybrids.