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

Abstract

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 Numedalslågen 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 (Fstrange: 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).

Contrasting patterns of gene diversity between microsatellites and mitochondrial SNPs in farm and wild Atlantic salmon

“…The generally higher number of nuclear alleles (allelic richness) in wild populations compared to farm populations observed in this study is in agreement with previous observations (Mjølnerød et al 1997;Norris et al 1999;Skaala et al 2004Skaala et al , 2005. The observation of a higher number of haplotypes in the mtDNA of farm salmon is surprising given that genetic drift is expected to have a significant impact on the genetic variation in the farm strains, due to low effective population size (estimated to 33-125 in the Aqua Gen breeding populations, Mork et al 1999), which is expected to be even lower for mtDNA.…”

“…One aspect rises from observations of lower genetic variation in farmed salmon compared to their wild counterparts (Mjølnerød et al 1997, Skaala et al 2004. Gene-flow from farmed salmon could ultimately decrease the genetic variation in wild populations, and thereby lower the adaptive potential (Hindar et al 1991).…”

Population genetics of the Pacific abalone (Haliotis discus hannai) in Korea inferred from microsatellite marker analysis

“…In this study, however, these founder effects may have been insignificant because there was no evidence of a bottleneck in the hatchery stocks. Besides founder effects, the genetic changes that were observed in the hatchery stocks compared to the wild populations were likely due to the artificial and natural selection that exists in the aquaculture environment (Mjolnerod et al, 1997). However, this selection could not be reflected using neutral markers such as the microsatellites in our study.…”

RAPD –PCR analysis of four coral reef fish species, genus cephalopholis (Family: serranidae) in the Red sea.

“…On the other hand, the use of RAPD assay for genetic analysis of fishes has been fairly limited in comparison to published reports on microorganism, plant and insect species (Park and Moran, 1994;Mjolnerod et al, 1997;Norris et al, 1999 andEl-Alfy et al, 2009).…”