James M. Long and William L. Fisher, Oklahoma Cooperative Fish and Wildlife Research Unit, 404 LSW, Oklahoma State University, Stillwater, OK 74078

Abstract. In an attempt to control an increasing spotted bass Micropterus punctulatus population, a differential harvest regulation was imposed on three black bass species in Skiatook Lake, Oklahoma. Spatial abundance and prey use patterns of adult largemouth M. salmoides, smallmouth M. dolomieui, and spotted bass were determined. In Spring 1997, fish were sampled by nighttime electrofishing to assess the potential for competition among these species. Skiatook Lake exhibited a longitudinal trophic state gradation from eutrophy in the upper end to oligotrophy in the lower end, based on chlorophyll-a concentrations. Largemouth bass catch per unit effort (CPUE) was similar among strata (P = 0.453). Smallmouth bass CPUE was significantly greater in the lower lake (P < 0.001) and was highly correlated with secchi depth (P < 0.001, r = 0.70). Spotted bass CPUE was significantly lower in Hominey Creek (P = 0.013), an uplake stratum, but was greater than both largemouth and smallmouth bass CPUE in most areas of the lake. Spotted bass and largemouth bass CPUE was not correlated with dissolved oxygen, conductivity, chlorophyll-a, or secchi depth. Largemouth and smallmouth bass consumed more fish whereas spotted bass ate more insect. The potential for competition exists even though black bass were segregated by prey and habitat usage.