AN alien fish from the Arctic ocean has been discovered in a Borders river.

The pink salmon, which weighed about 3.5lbs, was discovered in the River Tweed in August.

It is the fourth time the alien species has been reported in the river since 2007, according to the River Tweed Commission.

The species was also found in the River Tyne in the north-east of England earlier this year.

It is understood that this most recent find was full of eggs when it was removed from the river.

And there are fears for native species if the pink salmon was to start breeding.

The Environment Agency said the "unusual" discovery in the Tyne was "unlikely" to have a major impact.

Andrew Graham-Stewart, of the Salmon and Trout Association, said stocks would only be at risk if the fish were to start breeding.

He added: "Any species that are alien to Scottish rivers, one wouldn't want any influx of such a species, but it's only once a breeding population is established that we have got a major problem."

The River Tweed Commission said the fish found in the lower Tweed last month was "full of eggs".

It was removed from the river by the angler who caught it.

Ronald Campbell, a biologist for the Tweed Foundation, said the pink salmon would have come from north Norway, where rivers were colonised from Russian waters.