Jellyfish bloom reports soar from Cornwall to the Outer Hebrides

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From a “mile-long” swarm in Devon to warnings to swimmers in the Outer Hebrides, it seems jellyfish are difficult to ignore this summer.

High temperatures, calm and warm seas and packed beaches have resulted in large numbers of reports of jellyfish blooms around the UK coast, and combined with a glut of the plankton on which they feed, some are reaching record sizes, experts said.

At the fishing town of Brixham, Devon, one kayaker and photographer witnessed what he described as a mile-long mass of compass jellyfish. They have also been spotted in large numbers along the Cornish coast.

“They are very beautiful, with amazing markings, a whiteish jellyfish with black stripes running from the centre to the outside of their umbrella,” said Matt Slater of the Cornwall Wildlife Trust. “And really long tentacles, which can impart a sting. It hurts a bit but the pain dies off in about ten minutes.”

At the other end of the country, swimmers off the Isle of Lewis have had to contend with a group of lion’s mane jellyfish, which have a very nasty sting. Arthur Conan Doyle wrote a Sherlock Holmes short story in which one was responsible for a mysterious death. “We would ask people to keep away from this type of jellyfish and not touch them,” the Stornaway coastguard said.

Galway city council in Ireland issued a similar warning after the same species was spotted at Silverstrand beach. It advised swimmers to be extremely vigilant and to approach a lifeguard for assistance if stung.

The common moon jellyfish has been abundant in Devon, while in north-east England Sunderland city council issued a warning to swimmers and dog walkers after large numbers of blue jellyfish washed up on Seaburn beach.

Moon jellyfish

Coral Smith, a marine education officer at Devon Wildlife Trust, said: “This year the compass jellies have been very big, up to their maximum of about 30 centimetres. That’s unusual.” She credits this to plentiful plankton and the warmer weather. “And nice calm waters means they stick around. They are not getting washed out to sea again.”

Dr Victoria Hobson, a lecturer in marine ecology at Exeter University and a jellyfish expert, believes it is not an exceptional year for jellyfish blooms, but rather that the creatures are more visible.

“The weather’s been really lovely and it’s been quite calm, so better to see them. It’s been gloriously warm, and they like to come up to bask nearer the surface,” she said. With furlough, and staycations, “more people are out on the water, so a lot more eyes looking”.

Blooms come and go. One year one species will be abundant, the next another. “Blooms are caused by jelly fish polyps living on the sea bed feeding on plankton,” said Slater. “If there is plentiful food they will get fat and bud off into thousands of tiny baby jellyfish. You get huge swarms travelling and drifting in the ocean currents, and hoping they never end up on a beach.”

The advice to swimmers who have been stung is to scrape off any remaining tentacles using something similar to a credit card, and not to rub the area. They should rinse it with warm sea water, but avoid fresh water because it can cause further irritation. They should also be alert to the possibility of anaphylactic shock.

They should not urinate on the affected area. “That’s the old wives tale, but it doesn’t work for all jellyfish and it’s very embarrassing,” said Slater. “And if you’ve been stung by a portuguese man o’war it’s the worst thing you can do. It makes the pain ten times worse.”

Though not a true jellyfish, the portuguese man o’war is sometimes found in UK waters in late summer and early summer. It has a sting powerful enough to kill fish and occasionally even humans.

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