The first footage of an alien salmon spawning in UK waters has been recorded on the River Ness – sparking fears of a major threat to native species.
The pink, also known as humpback, salmon were filmed using Ness Salmon Fishery Board’s underwater cameras in the river near Inverness.
The fish are native to Pacific Ocean waters and have recently been caught by anglers in the rivers Ness, Dee and Spey.
They are believed to be related to pink salmon introduced to rivers in eastern Russia in the mid-1950s.
These fish have since been found in rivers in Scandinavian countries.
Chris Conroy, the board’s director, said: “This is undisputed proof that these non-native fish are attempting to spawn in our waters.
“We are forwarding this film to Marine Scotland to keep them aware of what is happening.
“It is, however, important to note that conditions in our rivers mean that the pink salmon eggs may not go on to successfully hatch – we will monitor the situation.”
Mr Conroy added: “We don’t know why they are here or whether this is a one-off year for them or, ominously, a more regular feature.
“While the risks are unknown in terms of their interaction with Atlantic salmon and other Scottish fish, they are unlikely to have a positive impact.”
Salmon and Trout Conservation UK and Professor Eric Verspoor, director of the Rivers and Lochs Institute at Inverness College UHI, have warned of the potential risk to native salmon.
Threats include competition for food.
Fears for Britain’s native salmon were first voiced about six years ago after several pink specimens were caught in UK waters – despite being 10,000 miles from their natural habitat.
The pink salmon is usually found in the chilly waters off Canada and Alaska where they are part of the staple diet of the grizzly bear. Their translucent eggs also make fine caviar.
One theory being looked into is that the pink salmon may have originated from the Barents Sea, where the Russians introduced thousands of them 40 years ago as part of a massive breeding programme.
Over the last 10 years some of these have successfully bred in rivers in Norway and Iceland and they may now be crossing the North Sea to Britain.
If they did colonise British waterways the results could be catastrophic for native wild Atlantic salmon.