October 26, 2021


Genetic material of Norwegian farm salmon being passed on to native salmon in Scotland, report states



A study by scientists of the Scottish government revealed how some Atlantic salmon populations in Scotland are increasingly Norwegian.


That's after DNA from fish farm escapees entered native groups through breeding.


Samples were taken from juvenile fish in more 250 sites between 2018 and 2019. Signs of "introgression" of genetic material were found at almost one quarter of the sites. While most were rated as "good" (almost 77%), 8% were graded as "poor" and 6% as "very poor", with researchers confirming that these were present in areas where fish firms are operating in sea lochs.


They span from the Shetlands to the Clyde. It's understood the health of wild fish salmon stocks may now be at risk.


"The genetic integrity of populations observed across (Scotland) was not uniform. Rather, signs of introgression were concentrated in areas of marine aquaculture production and freshwater smolt rearing. Outside these areas, little to no genetic changes were detected," the report stated.


"The available evidence indicates that introgression of genetic material from Norwegian farm salmon strains has altered the genetic composition of some populations within rivers near marine aquaculture production. The Shetland Isles, Hebrides and mainland west coast as far south as the Clyde were all notably affected."


The report added that interbreeding between escaped farmed Atlantic salmon and wild indigenous salmon creates a "disruption of the adaptive genetic composition of individuals and populations" which "can impact their fitness, resulting in a significant negative pressure on the viability of wild populations".


Genetic changes were found around the Clyde, Argyll, Lochaber, Wester Ross, West Sutherland, the Inner and Outer Hebrides and the River Shin and the River Ness.


The Marine Scotland paper was published earlier this month.


Salmon and Trout Conservation Scotland has called the results "a damning indictment" of the impact of salmon farming. Its director, Andrew Graham-Stewart, said: "Farmed salmon, the great majority of Norwegian origin, are essentially domesticated animals, bred for the table.


"When they interbreed with our wild salmon, the offspring are inevitably unsuited and unfit to survive in the wild. The future viability of wild salmon is dependent on their genetic integrity not being compromised by domesticated strains."


While there is no commercial fishing of wild salmon, more than 200 fish farms operate around Scotland. Together, they produce in excess of 150,000 tonnes of the product every year. High demand has seen the industry boom over the last 50 years and taken its value to more than £1billion, and there are ambitious plans for future growth.


However, critics have pointed to the loss of around 9.5 million farmed salmon per year – around 20% of the total stocks – from causes including lice, disease and the chemicals used to treat the problems, as well as the release of effluent into waters.


- The National