Scotland’s wild salmon stocks have DNA from escaped farmed fish, study finds

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AWARDED by conservationists, fishermen and diners, wild salmon is one of Scotland’s most iconic species and largest export.

This is after the DNA of escapees from fish farms entered indigenous groups through breeding.

Samples were taken from juvenile fish at over 250 sites between 2018 and 2019. Signs of “introgression” of genetic material were found at nearly a quarter of the sites. While most were rated as good (nearly 77%), 8% were rated as bad and 6% as very bad, with researchers confirming they were present in areas where fishing companies operate in the lochs. sailors.

They stretch from the Shetlands to the Clyde. It is understood that the health of wild fish and salmon stocks may now be at risk.

The report states: “The genetic integrity of populations observed across the country was not uniform. On the contrary, signs of introgression were concentrated in areas of marine aquaculture production and freshwater smolt culture. Outside of these areas, little or no genetic changes were detected.

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He continues: “The available evidence indicates that the introgression of genetic material from strains of Norwegian farmed salmon has altered the genetic makeup of some populations in rivers close to marine aquaculture production. The Shetland Islands, the Hebrides and the mainland west coast as far south as the Clyde were all particularly affected. ”

And he said the interbreeding between escaped farmed Atlantic salmon and native wild salmon creates a “disruption in the adaptive genetic makeup of individuals and populations” which “can impact their fitness, causing significant negative pressure. on the viability of wild populations “.

Genetic changes have been 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 document was released earlier this month.

The charity Salmon and Trout Conservation Scotland, whose boss is Prince Charles, called the results a “damning indictment” of the impact of salmon farming.

Its manager, Andrew Graham-Stewart, said: “Farmed salmon, the vast majority of Norwegian origin, are essentially domestic animals, raised for the table. When they interbreed with our wild salmon, the offspring are inevitably unsuitable and unfit to survive in the wild. The future viability of wild salmon depends on whether its genetic integrity is not compromised by domesticated strains.

Although there is no commercial wild salmon fishery, over 200 fish farms operate in Scotland. Together, they produce over 150,000 tonnes of product each year. Strong demand has boomed the industry over the past 50 years and has lifted its value to over £ 1 billion, and there are ambitious plans for future growth. Industry leaders, who have also had to deal with the consequences of Brexit and the Covid disruption, say it will be sustainable.

READ MORE: Loch Long Salmon: plans to develop Scotland’s first semi-closed fish farm

However, there has also been a series of controversies surrounding the use of imported eggs and the escape of farmed fish, which are kept in pens for about two years before being “harvested” for consumption. , as well as damaging outbreaks of parasitic lice which have, on the worst occasions, resulted in the dumping of large numbers of salmon.

Critics have pointed to the loss of about 9.5 million farmed salmon per year – about 20% of total stocks – to lice, disease and chemicals used to treat the problems, as well as discarding effluents in water.

The Scottish Salmon Producers’ Organization claims the industry is “the world leader in using cleaner fish such as wrasse and lumpfish” to “live among farmed salmon and remove and eat all sea lice. “, while the enclosures are equipped with heavy-duty high voltage. with “louse skirts” and other features to protect stocks.

This week, a representative of the organization told Ferret that it expects “nine out of ten salmon farms to meet” the “strict environmental standards” set by the Scottish Environmental Protection Agency on the pollution.


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