After the summer floods and freak weather comes a new jolt to our ecosystem: more than 100,000 salmon wiped out by jellyfish off the coast of Northern Ireland in a single attack.

The mauve stinger, which has caused Mediterranean beaches to be closed over the summer because of the fear of its potent sting, has arrived off British shores in unprecedented numbers.

Billions of the tiny jellyfish, covering an area of up to ten square miles (27 sq km) and up to 35ft (13.6m) deep, swamped fish-farm cages belonging to Northern Salmon Co and killed more than 100,000 salmon – valued at more than £1 million.

The attack took place last week at Glenarm Bay and Red Bay, Cushendun, off the scenic coastline of Co Antrim and has put the future of the Northern Salmon Co in jeopardy. “We are still assessing the full extent, but it’s a disaster,” said John Russell, the company’s managing director.

The salmon died from their wounds and from the stress of the jellyfish stings. At one stage staff tried to reach the cages in three boats, but such was the density of the jellyfish they struggled to get through and arrived too late to make a difference.

Mr Russell said: “In 30 years, I’ve never seen anything like it. It was unprecedented – absolutely amazing. The sea was red with these jellyfish and there was nothing we could do.”

The company sells its salmon to some of London’s finest restaurants. Last year, the Queen had its salmon cooked for her on her 80th birthday by the Irish chef Richard Corrigan. It is also exported to hotels and restaurants in France, Belgium, Germany and the United States.

Officials from the Northern Ireland Department of Agriculture’s fisheries division have carried out a full investigation and talks have been held with Michelle Gildernew, the Agriculture Minister, in an attempt to put together a financial package to save the farm and the jobs of its 12 staff.

Mr Russell said that the attack, on Tuesday and Wednesday of last week, had left him devastated. “It’s touch and go if we can survive. Our salmon is a premier product which fronts up the seafood industry in Northern Ireland and everything must be done to protect it. It’s really important for the seafood industry we get up and going again, because we’ve taken a huge financial hit.”

Fish farms around Britain and the West Coast of Ireland have been attacked before by jellyfish, but the type blown towards the Antrim coast by winds from the North have never been recorded in the area before. It is extremely rare for mauve stingers to visit the colder waters around the British Isles.

Mr Russell, from Fort William, Scotland, who took over as the company’s managing director three days before the attack, said: “I have never experienced such concentrations of jellyfish spread over such a wide area. The vastness was unbelievable.

“It’s a disaster for this company. You cannot legislate for something like this.”

Scientists attributed the increase in swarms of mauve stingers to the warming of the seas and the decline in their predators, including sunfish and trigger fish, through over-fishing.

Red tide

— Pelugia noctiluca is uncommon in British and Irish waters, but may be found anywhere over deep water off the west and north coasts

— May grow up to 10cm in diameter. Varies from pale red to mauve-brown or purple

— Identified by bell of mushroom shape. Exumbrella and tentacles are covered in pink or mauve nematocysts

— Has 16 marginal lobes, 8 marginal sense organs, and 8 hair-like marginal tentacles

— Also called the nightlight jellyfish, because it produces a blue-green luminescent mucus, most often seen as a glow in the wakes of ships

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