Lens Protein Polymorphisms in Hatchery and Natural Populations of Brook Trout, Salvelinus fontinalis (Mitchill)

Lens protein phenotype and allele frequencies of three autosomal loci were analyzed by acrylamide gel electrophoresis for 1,164 specimens from four hatchery populations of brook trout, Salvelinus fontinalis (Mitchill), each representing combined progenies from random matings of hundreds of parents. A deficiency of heterozygous genotypes at one locus, according to Hardy-Weinberg analysis, may indicate a degree of inbreeding in the hatchery environment. Allele frequencies of the lens protein variations appeared to be relatively stable from year to year within a particular hatchery. Gene frequency analyses for the lens protein variations disclosed that brook trout populations from some of the different hatcheries were distinguishable from each other. Analyses of the lens proteins for 547 specimens from nine natural populations of brook trout revealed no genetic divergence in these small isolated populations. A length-frequency analysis of one population indicated that allele frequencies were independent of length classes. Evidence was presented suggesting that a distance greater than 300 yards may act as an isolating mechanism leading to genetic divergence of a brook trout population in one small stream. Gene frequency analyses for the lens protein variations disclosed that some of the brook trout natural populations from different areas sampled were distinguishable from each other.