Dense shoals of tiny jellyfish have killed almost one million salmon at fish farms in the Western Isles.

It is thought that the jellyfish - known as Solmaris - may have found their way to Scottish waters from the Pacific Ocean.

They killed the salmon by stinging them and clogging up their gills.

We have never suffered this before - this has set us back four months

Alan Anderson Western Isles Sea Foods

Fish with an estimated value of more than �2m were destroyed at two farms off the Isle of Lewis.

Vast blankets of jellyfish moved up the sea lochs where the salmon cages are moored.

The larger fish were suffocated while smaller ones were stung to death.

Western Isles Sea Foods said almost all the fish at the two farms had been destroyed.

Managing director Alan Anderson said 750,000 fish were lost at one site and 150,000 at the other, meaning a loss to the firm of more than �2m.

Fully grown

"It's a disaster to lose that number of fish - it's almost a million fish but they're insured and business continues as normal.

"We have never suffered this before - this has set us back four months."

Another company lost 400 tons of salmon which were fully grown and ready for market.

The salmon were worth an estimated �3m

The dead fish are being taken away by boat to a fish meal factory in Shetland.

It is thought the jellyfish made their way into the Atlantic from the Pacific by attaching themselves to vessels passing through the Panama Canal in Central America.

Other species of jellyfish in the shoals on the south east coast of Lewis are known to be poisonous and can kill fish by injecting histamine through their stings.

Salmon farms have suffered losses from jellyfish in the past.

However, the latest attack has been described as "unusually severe".