GENETIC DIFFERENTIATION AND HYBRIDIZATION BETWEEN STOCKED HATCHERY AND NATIVE BROOK TROUT IN GREAT-SMOKY-MOUNTAINS-NATIONAL-PARK

Starch gel electrophoresis was used to examine the protein products of 34 presumptive loci in nine populations of brook trout Salvelinus fon tinalis from Great Smoky Mountains National Park and in two brook trou t hatchery strains that were derived from northeastern U.S. population s and used extensively for stocking in the southern Appalachian Mounta ins. Five of the streams sampled had not been stocked and presumably c ontained only native brook trout. Three other streams contained native populations but also had been stocked, and the remaining stream origi nally was devoid of natives and presumably contained only introduced b rook trout. Mean genetic similarity was high among the native populati ons (IBAR = 0.985 +/- 0.017 SE) and among the hatchery-derived populat ions (IBAR = 0.986 +/- 0.003). Mean genetic similarity between the nat ive populations and hatchery stocks was 0.906 +/- 0.024. These results are consistent with previous studies suggesting that native brook tro ut in the southeastern United States are taxonomically distinct from n ortheastern brook trout. Genotypes at diagnostic loci demonstrate that introgressive hybridization has occurred between hatchery and native trout in all three stocked populations. Average individual heterozygos ity was lowest in the native populations (H-0BAR = 0.025), highest in the hatchery stocks (H-0BAR = 0.112), and intermediate in the stocked populations (H-0BAR = 0.053).