Samples of salmon Salmo salar from the River Kachkovka and the River N
ilma in northern Russia were analysed by starch gel electrophoresis an
d compared to three Norwegian stocks, the Neiden river in northern Nor
way and Oyreselv and Hopselv rivers on the west coast. The comparison
included the following polymorphic loci: AAT-4*, IDDH-2*, IDHP-3*, MDH
-3,4*, MEP-2*, ESTD* as well as the newly discovered polymorphic loci
FBALD-3* and TPI-3*. Samples were run side by side on gels, and the al
leles found in the Russian stocks were the same as those found in the
Norwegian stocks, although the electrophoretic methods used lead to di
fferences in designations of alleles. A polymorphism in ESTD* which in
volves a slow allele was commonly observed in the three northern popul
ations of the Nilma, Kachkovka and Neiden rivers. This allele was abse
nt 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 fr
equencies in the northern populations. Thus, the variability observed
at these two loci indicates a barrier to gene flow between the norther
n salmon stocks and the more southern stocks in the East Atlantic area
. (C) 1998 The Fisheries Society of the British Isles.