Scotland is hoping awareness will mean its waters will remain clean
On the River Ogna in Central Norway a small group of local anglers have cast aside their rods and are using nets to save as many fish as they can.
The salmon and trout tangled in their green netting are the lucky ones.
They're disinfected in a tank of salty water and then moved to safety.
The fish which got away are about to die, when officials dose 18 km of the river here with poison.
They're trying to kill off a parasite called Gyrodactylus Salaris (Gs).
Around 40 of Norway's 400 or so rivers have been infected with Gs. In those places it has led to the decimation of the wild Atlantic salmon.
And Scotland's ministers have already outlined a plan to cull whole river systems, should the worst happen, and the parasite arrive in any Scottish waters.
The Scottish government has warned it will not sit back and allow the parasite to devastate this iconic fish, and harm such an important Scottish industry. But it's hoping it'll never have to call the plan into action.
Gs is "a really bad thing", says Norwegian wildlife official Trond Haukebo. "It harms the small fish, not the big ones. They get infections and die slowly. It is not a nice way of dying."
So I watched as scientists released thousands of litres of a chemical called Rotenone into the water.
They are quick to reassure us that it breaks down quickly, and is not toxic to humans, other animals or plants.
But as the chemical cloud drifts downstream it will kill every fish and parasite it embraces.
According to Haukebo the theory is that "if you take away the fish, you take away the parasite".
The treatment is precisely timed. A team of locals on boats - and guided by divers in drysuits - spray rotenone onto both banks of the river.
They are trying to ensure no rock or small pool of water is left untreated. They cannot afford to let a single salmon fry survive.
Other teams wade through the waters gathering as many of the dead fish as they can. Their black bin bags full of dead fish are taken away for analysis.
Watching it brings to mind a military operation. The rotenone treatment has taken officials years to plan. The river and all its seeps and creeks are all precisely mapped. Every phase of the operation has to happen at exactly the right time. Even then it's not guaranteed to succeed.
Video from Norway's river treatment programme
Norwegian locals seemed supportive of the treatment programme.
They want their river to be healthy again and parasite free. But in previous years rotenone treatments have attracted the attention of environmentalists from Oslo.
Some might perhaps think this treatment is a little extreme.
"Well, it is," said Ketil Scar from the National Veterinary Institute.
"But it would be more extreme to lose a species because of a parasite.
"If we had any other means we would do it, but the problem is not using rotenone, it is the parasite."
This is not work these Norwegian Nature management officials do frivolously. It is a last resort.
The fish is iconic to the Scandinavian country. They are determined to save their wild Atlantic salmon and to stop the parasite spreading.
Anton Rikstad is the local fisheries manager, and in charge of the River Ogna. He said it had gone "from a very good salmon river to an empty river in 30 years".
"It has been a catastrophe," he added.
The parasite has taken a large toll on Norway's salmon stocks
I hope you don't get it in Scotland."
Of course most of Norway's rivers have a clean bill of health.
They are keen to keep it that way, as restoring an infected river and restocking from a dedicated salmon gene-bank is slow and expensive work.
The Scottish Government points to the millions of pounds of public money which Norway has to spend each year to control the parasite.
Richard Lochhead, the Scottish cabinet secretary for rural affairs, said all Scottish fresh water users needed to be aware of the dangers of spreading the parasite if they had been near foreign infected waters.
"Scotland has taken a responsible, planned and proactive approach to reduce the risk of Gs arriving in Scotland and has worked with a wide range of other organisations to prepare a detailed contingency plan," he said.
The Norwegians' message to other countries, like Scotland, is that prevention is better than cure. That it's far better to stop this devastating parasite infecting the rivers in the first place.
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