UK coasts on alert for return of killer jellyfish

Scientists mobilise to tackle billions of mauve stingers that wiped out an Ulster fish farm and left 14,000 bathers needing treatment in Spain

Scientists have launched an urgent investigation into the mauve stinger jellyfish which recently wiped out £1m worth of salmon at fish farms in Northern Ireland. They fear that mass invasions of the tiny purple creatures could return to British waters in the next few years with devastating consequences along coasts.

Many Scottish fish farms would be at risk from the jellyfish, which are so small they can drift through the mesh of the salmon cages but which can nevertheless deliver powerful stings that are far worse than a wasp's. These are often deadly for young salmon.

In recent years plagues of mauve stingers (Pelagia noctiluca) - which vary in dimensions from a 10p piece to the size of a clenched fist - have affected the Mediterranean. Last November's infestation was the first major incident affecting British waters, however. Many scientists suspect that global warming, which is heating oceans, is most probably the principal cause of the appearance of massed jellyfish flotillas in the Irish Sea.

In the case of last November's bloom, billions of jellyfish, in a layer 35ft deep and covering 10 square miles of water, drifted into Glenarm Bay in Antrim and wiped out 120,000 salmon in the local fish farm. Workers tried to get to the caged salmon, but the density of the jellyfish in the sea prevented them reaching the fish in time. A second jellyfish swarm was sighted off Scotland but there were no reports of it inflicting damage.

'The trouble is that we know so little about these jellyfish,' said Jon Houghton, a marine biologist from Swansea University. 'Until recently, they were viewed as bags of water that had little or no impact on our ecosystem. Now we need to learn, very quickly, about their behaviour and about their breeding patterns in our waters.'

The Natural Environment Research Council has provided Houghton and his team with a special emergency grant of £50,000 to launch a study into the mauve stinger. Work began on the project three weeks ago, on ferries on the Irish Sea. 'We need to get some basic data about numbers, and the easiest and quickest way to do that is simply to send researchers out on the ferries that come out of Fishguard, Holyhead, Larne, Rosslare and other ports,' added Houghton.

'For the past few weeks, they have been standing on deck looking at the sea and counting jellyfish. That is how we are getting a baseline figure for their numbers.'

This work is to be followed up over the next few months by biologists who will sail on British research boats and trawl the Irish Sea and North Atlantic in a careful pattern in an attempt to determine the numbers and the health of mauve stingers. Researchers will fly over coastal areas to study jellyfish blooms as well.

'We need to know whether last year's jellyfish bloom, which was unprecedented in its size, is going to occur again in the near future,' said Dr Tom Doyle, of the Coastal and Marine Resources Centre at University College, Cork. 'To do that we need basic ecological data that we simply do not have at present.'

Blooms of Pelagia noctiluca have been documented in the past and are known to turn the sea red by day and emit flashes of purple light in the dark. But the intensity of November's bloom was remarkable, producing eerie glows all along the coast. 'The bloom was so thick it lit up the beaches at night,' said Doyle.

'However, in one sense, we were lucky,' added Doyle. 'In November no one would have been swimming in the Irish Sea. In summer there could have been real problems.

'For example, in August 2006 a massive mauve stinger bloom appeared off the Spanish coast and 14,000 people who had been swimming there needed treatment. We need to know if that sort of thing could happen here if the mauve stingers come back.'


Robin McKie, science editor

The GuardianTramp

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