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Seven samples, each consisting of approximately 50 Atlantic salmon, were collected from five marine farms in Norway. These farms reported to rear fish originating from the same commercial breed; however, all samples followed a unique route of production from breeder to marine farm via egg, fry and smolt producers. A group of farmed escapees ( n=50) were also captured. Following genotyping with 18 microsatellite loci, the global FST was 0.083, and pair-wise values were as high as 0.158. Four clusters, with varying degrees of genetic differentiation, were identified among samples from the farms, and the source of the escapees was identified successfully. It is suggested that the genetic differences observed among samples from the farms were created through the process of genetic drift, facilitated by parallel sub-strains, extensive within-strain selection and low to moderate numbers of adults contributing to batches of eggs. In conclusion, this study has demonstrated that genetic identification of escaped Atlantic salmon, back to the farm of origin, may be possible even when farms rear fish reported to originate from a single breeder. [ABSTRACT FROM AUTHOR]

This study presents a molecular genetic characterization of Atlantic cod reared in commercial marine farms. Samples consisted of approximately 47 fish collected from nine cages located on four farms throughout Norway. In addition, 28 farmed escapees were recaptured in the sea (443 fish in total). Nine microsatellite loci and the Pan I gene were analysed, revealing a total of 181 alleles. Each sample contained 43–63% of total allelic variation. Comparing variation with published data for wild cod indicates that lower genetic variation exists within single cages than in wild populations. Significant linkage disequilibrium was observed amongst pairs of loci in all samples, suggesting a low number of contributing parental fish. Global FST was 0.049, and the highest pairwise FST value (pooled loci) was 0.085. For single loci, the Pan I gene was the most diagnostic, displaying a global FST of 0.203. Simulations amongst the samples collected on farms revealed an overall correct self-assignment percentage of 75%, demonstrating a high probability of identifying individuals to their farm of origin. Identification of the 28 escapees revealed a single cage as the most likely source of origin for half of the escapees, whilst the remaining fish were assigned to a mixture of samples, suggesting more than one source of escapees. [ABSTRACT FROM AUTHOR]

Glover, K. A., Skilbrei, O. T., and Skaala, Ø. 2008. Genetic assignment identifies farm of origin for Atlantic salmon Salmo salar escapees in a Norwegian fjord. – ICES Journal of Marine Science, 65: 912–920.This study represents the first example of genetic assignment being used to identify the farm of origin for escaped Atlantic salmon. Following reports by local fishers of escaped farmed salmon in Romsdalfjord, western Norway, baseline samples were collected from 16 cages located on seven operational farms. The baseline samples, in addition to 29 escapees, were screened for 15 microsatellite loci. Pairwise FST values between baseline samples varied from <0.001 to 0.154, indicating variable but significant genetic differences among them. Direct assignment of the escapees (data from 13 informative loci) demonstrated that the most likely origin of 21 of them was from a single baseline sample (5I) collected at one farm. At a probability of 0.01, between 25 and 29 of the escapees were rejected in 12 baseline samples, 19–21 escapees were rejected from another three baseline samples, and only seven of the escapees were rejected from baseline sample 5I. Consequently, these data demonstrate that most of the escapees most likely originated from a single farm, and importantly, that 15 of the 16 baseline samples could with high probability be excluded as donors for most of the escapees recaptured in the area. [ABSTRACT FROM PUBLISHER]

Samples of wild and domesticated salmon in Norway were genotyped at 12 microsatellite loci to compare allelic variability and investigate the potential of microsatellite markers for identification of individuals. The following loci were amplified: Ssa20, Ssa62NVH, Ssa71NVH, Ssa90NVH, Ssa103NVH, Ssa105NVH, SsaF43; Ssa20.19; Ssa13.37; SsOSL85; Ssa197; Ssa28. All domesticated strain samples displayed reduced variability compared to wild salmon. On average 58% of the allelic richness observed within the four wild stocks were present in the samples taken from domesticated strains. No systematic differences in heterozygosity were observed between samples representing the two groups.Pairwise genetic distances, as estimated by Fst values and Nei [1978] was 2–8 times higher among domesticated strains than among wild strains. Among the wild stocks, the highest genetic distances were observed between the river Neiden, located in northern Norway, and the other wild stocks located in the southwest of Norway.Assignment tests indicated that the wild and domesticated salmon could be distinguished with high precision. Less than 4% of domesticated salmon were misassigned as wild salmon, and less than 3% of wild fish were misassigned as domesticated salmon. Fish from individual domesticated strains were identified with similarly high precision. Assignment to wild salmon stocks was less accurate, with the exception of the sample taken from the river Neiden, for which 93% of the individuals were correctly assigned. [Copyright &y& Elsevier]