GENETIC-DIFFERENCES BETWEEN 2 WILD AND ONE FARMED POPULATION OF ATLANTIC SALMON (SALMO-SALAR) REVEALED BY 3 CLASSES OF GENETIC-MARKERS

Genetic diversity within and between two wild and one farmed populatio n of Atlantic salmon was estimated by 12 variable enzyme loci, three s ingle locus-and one multilocus DNA minisatellite probe. The farmed sal mon were fifth-generation fish from one of the principal commercial st rains in Norway and the wild salmon were from the rivers Numedalslagen and Tana, Norway. All three classes of markers detected significant d ifferentiation between the populations, with the farmed population bei ng genetically most divergent. The farmed fish showed less genetic var iability 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 leve l of heterozygosity within the farmed population. Estimates of average heterozygosity within populations were almost identical for single lo cus and multilocus minisatellites (0.558 and 0.548, respectively), whi ch 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 minisatellite s (F-st range: 0.106-0.135). Our results show that fifth generation fa rmed Atlantic salmon differ significantly from wild salmon in loci oth ers than those chosen for selection in the breeding program. The study also suggests that the choice of genetic markers for studies of Atlan tic salmon depends on the aim of the study (within-versus between-popu lation variability).