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UK coasts on alert for return of jellyfish

Scientists have launched an urgent investigation into the mauve stinger jellyfish that recently wiped out US$2 million 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 often deadly for young salmon.

In recent years plagues of mauve stingers, or Pelagia noctiluca, have affected the Mediterranean. But last November's was the first major incident affecting British waters. Scientists suspect that global warming is probably the principal cause of the appearance of jellyfish flotillas in the Irish Sea.

In the case of November's bloom, billions of jellyfish, in a layer 11m deep and covering 26km2 of water, drifted into Glenarm Bay in Antrim and wiped out 120,000 salmon at a fish farm.

"The trouble is that we know so little about these jellyfish," said Jon Houghton, a marine biologist from Swansea University, Wales. "Until recently, they were viewed as bags of water that had little or no impact on our ecosystem."

The UK's Natural Environment Research Council has provided Houghton and his team with a special emergency grant to launch a study into the mauve stinger.

Work began on the project last month, on ferries on the Irish Sea between the British mainland and Ireland.

"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," Houghton said. "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 also fly over coastal areas to study jellyfish blooms.
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