Allozyme variation in Atlantic salmon from the British Isles: associations with geography and the environment

Data on geographical variation in allele frequencies at enzyme coding loci in Atlantic salmon from the British Isles were collated from published and unpublished sources. Statistically significant differences in allele frequencies were found among samples both within and among river systems, suggesting that the Atlantic salmon in the British Isles is not a panmictic population and that even within major river systems it cannot be treated as a single genetic stock for fisheries management purposes. Although there was some evidence of regional differences in the frequency of some rare alleles, most single-locus variation did not show strong geographic patterns, with the exception of the AAT-4* locus at which allele frequencies had a significant latitudinal cline. There was some evidence for the existence of genetically-distinct celtic and boreal races of Atlantic salmon in the British Isles as previously has been suggested. Multiple regression analyses revealed associations between genetic variation and local environmental conditions (i.e. between variation at MEP-2* and both temperature and local river gradient), providing additional evidence for adaptive population divergence in the species.