Genetic Protein Variation in Natural Populations of Atlantic Salmon (Salmo salar) in Scotland: Temporal and Spatial Variation

Levels of temporal and spatial genetic heterogeneity within and among Atlantic salmon (Salmo salar) populations in Scotland were assessed through starch-gel electrophoretic analysis of variation at 30 protein-coding loci. Over three year-classes the level of temporal variation within populations was generally nonsignificant, although significant heterogeneity among year-classes was found at some loci at some locations. Hierarchical analysis of gene diversity showed that 97.6% of the genetic diversity was found within single sites, with the remaining diversity distributed among sites. While there was no evidence of subpopulation differentiation among a number of samples of Atlantic salmon from the River Tweed system, significant genetic heterogeneity was observed among samples from different river systems within Scotland. Comparison of the levels of among-population heterogeneity in the Atlantic salmon with those found in the closely related brown trout (Salmo trutta) over a similar geographical area shows the Atlantic salmon to be relatively genetically homogeneous.