Previous studies of the ESTD* isozyme locus in the Atlantic salmon show the *80 allele to be absent across the species’ European range, with the exception of northern Russia, whereas the allele is nearly fixed in North American populations. The allele was found in samples from 15 out of 18 rivers on the Kola Peninsula and White sea coast and had frequencies that ranged from 0·017 to 0·363. Typing of fish in nine of these rivers for mtDNA variation in the ND1 gene region found variation characteristic of North American salmon in three Kola Peninsula populations and is the only part of Europe where such variants have been detected. The study area was completely glaciated during the late Pleistocene period and the restriction of the European distribution of these ESTD* and mtDNA variants to this area suggests that salmon that colonized the Russian Arctic coast rivers included fish of North American origin after the Pleistocene glacier had retreated.
Makhrov, AA., Verspoor, E., Artamonova, VS., & O'Sullivan, M. (2005). Atlantic salmon colonization of the Russian Arctic coast: pioneers from North America. Journal of Fish Biology, 67, 68-79. https://doi.org/10.1111/j.0022-1112.2005.00840.x