The genetic background of Stofnfiskur breeding lines of farmed Atlantic salmon

Karlsson, S., Spets, M.H., Eriksen, L.B & Ólafsdóttir, G. 2017. The genetic background of Stofnfiskur breeding lines of farmed Atlantic salmon - NINA Report 1401. 17 pp. Stofnfiskur is a breeding company of Atlantic salmon located in Iceland, and delivers salmon eggs to the fish farming industry, including the Norwegian aquaculture industry. Escaped farmed salmon is considered one of the most important threats to wild salmon populations. Foreign genetic origin of the farmed salmon may possess an extra negative effect on wild salmon populations and is therefore discouraged in Norwegian legislation, and in NASCO guidelines. Documentation of the genetic origin is mandatory before approved to be used in Norwegian aquaculture. According to the information from Stofnfiskur, the Stofnfiskur breeding lines are of Norwegian origin and is a mixture of farmed salmon from the three major breeding companies in Norway: at that time Bolaks, Mowi and the National selective breeding program. The Norwegian Environment Agency has ordered a molecular genetic analysis to confirm the Norwegian origin. DNA extraction and genotyping at 96 Single Nucleotide Polymorphisms (SNPs) of fish from the Stofnfiskur breeding lines and of wild salmon from five Icelandic rivers was conducted at Matís, Icelandic Food and Biotech R&D, Iceland. We compared the genetic profiles of salmon from Stofnfiskur and the wild Icelandic salmon with the large database of Norwegian wild salmon at NINA. As a group, the Stofnfiskur salmon was genetically similar to the southern phylogenetic group in Norway and distinctively different from the Icelandic wild populations. At the individual level, 186 of 187 fish (99.5%) from Stofnfiskur assigned genetically to Norwegian rather than Icelandic wild populations, and one fish assigned with a high relative probability (98.4%) to Iceland populations. One out of 362 Icelandic wild salmon assigned to Norway rather than to Iceland, and two out of 2087 Norwegian salmon assigned to Iceland. Our analyses confirm that the salmon at Stofnfiskur is of Norwegian origin. Because Stofnfiskur is now in use in fish farms in Norway, we were also interested in to what extent we could trace this fish in events of escapes and interbreeding with wild Norwegian salmon. We used the same genetic markers and statistical analyses that are currently in use in Norway. The salmon from Stofnfiskur were not as genetically different from the Norwegian wild salmon as the current Norwegian breeding