Genetic Differentiation and Hybridization between Stocked Hatchery and Native Brook Trout in Great Smoky Mountains National Park

Abstract

Starch gel electrophoresis was used to examine the protein products of 34 presumptive loci in nine populations of brook trout Salvelinus fontinalis from Great Smoky Mountains National Park and in two brook trout hatchery strains that were derived from northeastern U.S. populations and used extensively for stocking in the southern Appalachian Mountains. Five of the streams sampled had not been stocked and presumably contained only native brook trout. Three other streams contained native populations but also had been stocked, and the remaining stream originally was devoid of natives and presumably contained only introduced brook trout. Mean genetic similarity was high among the native populations ( = 0.985 ± 0.017 SE) and among the hatchery-derived populations ( = 0.986 ± 0.003). Mean genetic similarity between the native populations and hatchery stocks was 0.906 ± 0.024. These results are consistent with previous studies suggesting that native brook trout in the southeastern United States are taxonomically distinct from northeastern brook trout. Genotypes at diagnostic loci demonstrate that introgressive hybridization has occurred between hatchery and native trout in all three stocked populations. Average individual heterozygosity was lowest in the native populations ( = 0.025), highest in the hatchery stocks ( = 0.112), and intermediate in the stocked populations ( = 0.053).