A minisatellite DNA marker for discriminating between European and North American Atlantic salmon (Salmo salar)

A highly discriminatory and practical nuclear DNA genetic marker that can distinguish between Atlantic salmon (Salmo salar) of European and North American origin is described. Screening of 2847 European and 247 North American Atlantic salmon from much of its geographic range for variability at a minisatellite locus, Ssa-A45/2/2, revealed the continental stocks to be almost fixed for two different-sized, easily discernable alleles. Virtually all European Atlantic salmon were homozygous for a 3.00-kb allele (frequency > 0.999), while a smaller 2.77-kb allele (frequency = 0.946) predominated in all North American populations. Whereas the 2.77-kb allele was found exclusively in North American salmon, an allele indistinguishable in size from the 3.00-kb European diagnostic allele was also observed at low frequency (0.036) in North American fish. Eight other continent-specific rare alleles (highest frequency = 0.006) were also observed. The results suggest that little, if any, natural gene flow occurs between the two continental groups of Atlantic salmon.