We are grateful to Fred Utter and three anonymous reviewers for helpful comments on the manuscript. Ivan G. Pola contributed assistance in the laboratory, and Jerónimo de la Hoz provided Atlantic salmon samples. We are grateful to Fernando Ayllon for providing genotypes of the 1988 and 1996 samples. This study was financially supported by European Union Interregional European Funds (INTERREG) Project Atlantic Arc Resources (AARC). J.L.H. held a research contract funded by the Foundation for the Promotion in Asturias of Applied Scientific Research and Technology (IB09-0023); G.M.-S. was supported by European Union Framework 7 Project Salmon at Sea- (SALSEA-) Merge.