Populations of largemouth bass (Micropterus salmoides) in Oklahoma reservoirs were sampled in 1986 and 1987 to determine the degree of introgression of Florida largemouth bass (M. s. floridanus), introduced over a 16-year period, into populations of native northern largemouth bass (M. s. salmoides). Florida subspecific alleles were present in 28 of 30 populations (93%) and were found in >50% of the fish from 8 (27%) reservoirs. Correlations with selected physical and biological parameters indicated that the percentage of bass with Florida alleles increased as the size of fish stocked increased and as cold weather and water level fluctuation decreased. Reservoirs in southern portions of the state with stable water levels that were stocked with fingerlings > 100 mm in length at rates > 25/ha for several consecutive years had the highest degrees of Florida allele introgression into existing bass populations.
