Abstract: DNA sequences from the mitochondrial gene cytochrome oxidase subunit I (mtDNA COI) were used to estimate the genetic variability in two wild populations and two cultured populations of the hard shelled mussel, Mytilus coruscus. Thirty haplotypes were identified in the four populations. The cultured populations exhibited a lower number of haplotypes and genetic diversity than those of the wild populations, suggesting that a small number of effective founding breeders contributed to the genetic variation of the cultured populations. No significant differentiation was observed between the cultured population and local wild population, implying that persistent gene flow occurred in these populations. This genetic survey is intended as a baseline for future genetic monitoring of M. coruscus aquaculture stocks.