Allozyme variation in populations of Atlantic salmon located throughout Europe: diversity that could be compromised by introductions of reared fish

A comprehensive understanding of the population structure of Atlantic salmon (Salmo salar L.) throughout the species range would help to determine the impact that cultured fish could have on wild populations. To help achieve this aim, Atlantic salmon samples were obtained from 14 locations throughout Europe (including Iceland) and screened for variation at 32 allozyme loci. A sample was also obtained from Canada to serve as an out-group. Seventeen allozyme loci were found to he variable in one or more of the populations studied and three, (s)AAT-4*, IDDH-2*, and mMEP-2* were variable across the range. This is the widest-ranging study to include ESTD-2*, FBALD-3*, and TPI-3*, which combined contributed 28% to the total genetic diversity detected. Genotype frequencies complied with Hardy-Weinberg expected proportions. Over all loci, highly significant heterogeneity was observed between samples. Alternate alleles segregating at ESTD-2* were found to be largely exclusive to Europe or North America. A neighbour-joining dendrogram was constructed to visualize relationships between populations and was consistent with previous findings that revealed Baltic and European clusters, with the Canadian population being the most genetically distinct. A significant association was observed between geographic and genetic distance. which suggests the potential for local adaptation, thus highlighting the need for conservation of wild populations. (C) 1997 International Council for the Exploration of the Sea.