Genetic Differences Between Two Wild and One Farmed Population of Atlantic Salmon (Salmo salar) Revealed by Three Classes of Genetic Markers

Abstract

Mjelnerad, I. B., Refseth, U. H., Karlsen, E., Balstad, T., Jakobsen, K. S. and Hindar, K. 1997. Genetic differences between two wild and one farmed population of Atlantic salmon (Salmo salar) revealed by three classes of genetic markers. Hereditas 127: 239-248. Lund, Sweden. ISSN 0018-0661. Received April 7, 1997. Accepted August 21, 1997 Genetic diversity within and between two wild and one farmed population of Atlantic salmon was estimated by 12 variable enzyme loci, three single locus- and one multilocus DNA minisatellite probe. The farmed salmon were fifth-generation fish from one of the principal commercial strains in Norway and the wild salmon were from the rivers Numedalslagen and Tana, Norway. All three classes of markers detected significant differentiation between the populations, with the farmed population being genetically most divergent. The farmed fish showed less genetic variability than the wild populations, as all techniques revealed a lower (14 %-45 %) number of variable bands/alleles in this group. However, only multilocus DNA fingerprinting detected a significantly lower level of heterozygosity within the farmed population. Estimates of average heterozygosity within populations were almost identical for single locus and multilocus minisatellites (0.558 and 0.548, respectively), which were more than three times higher than for polymorphic allozymes (0.162). Estimates of interpopulation genetic differentiation, however, gave highly concordant results between the allozymes and minisatellites (Fst range: 0.106-0.135). Our results show that fifth generation farmed Atlantic salmon differ significantly from wild salmon in loci others than those chosen for selection in the breeding program. The study also suggests that the choice of genetic markers for studies of Atlantic salmon depends on the aim of the study (within- versus between-population variability).