Genetic differences among brown trout, Salmo trutta, stocks and their importance for the conservation and management of the species

Abstract

SUMMARY. 1. Review of published studies on genetic variation, as shown by electrophoretic studies of protein variation, in natural brown trout (Salmo trutta L.) populations from Britain and Ireland, Finland, France, Greece, Iceland, Norway, Sweden, U.S.A. and U.S.S.R., revealed abundant geographical variation in gene frequency with individual populations containing only a limited part of the gene diversity of the species.2. Thirty‐eight (54%) of the seventy gene loci examined have been found to be polymorphic in the species with an average population showing polymorphism at 16% of its loci (range 0‐34.8%).3. The brown trout is naturally subdivided into a large number of reproductively isolated and genetically distinct populations within, as well as among, drainages.4. Two independent post‐glacial colonizations, by genetically distinct races, followed by independent evolution in separate drainages over the past 13,000 years is seen as responsible for the genetic diversity of brown trout in north‐western Europe.5. Many genetically unique populations have been lost in the past 100 years and there is an urgent need to identify and conserve the remaining genetic diversity. Genetically unique populations are an irreplaceable resource for rational management in relation to angling and future aquaculture potential.