Genetic comparison of salmon from the White Sea and north‐western Atlantic Ocean

Samples of salmon Salmo salar from the River Kachkovka and the River Nilma in northern Russia were analysed by starch gel electrophoresis and compared to three Norwegian stocks, the Neiden river in northern Norway and Oyreselv and Hopselv rivers on the west coast. The comparison included the following polymorphic loci: AAT-4*, IDDH-2*, IDHP-3*, MDH3,4*, MEP-2*, ESTD* as well as the newly discovered polymorphic loci FBALD-3 *a nd TPI-3*. Samples were run side by side on gels, and the alleles found in the Russian stocks were the same as those found in the Norwegian stocks, although the electrophoretic methods used lead to diVerences in designations of alleles. A polymorphism in ESTD* which involves a slow allele was commonly observed in the three northern populations of the Nilma, Kachkovka and Neiden rivers. This allele was absent in the other Norwegian stocks and in a major brood stock of farmed salmon in Norway. The IDHP-3*116 allele was found in unusually high frequencies in the northern populations. Thus, the variability observed at these two loci indicates a barrier to gene flow between the northern salmon stocks and the more southern stocks in the East Atlantic area.