At least two people have been stung and the authorities are advising caution as thousands of jellyfish blow ashore on Wellington's south coast.
Island Bay and other south coast beaches were coated with at least two species of jellyfish yesterday, including the potentially deadly bluebottle or pacific man o' war.
Julian Hodge, of Island Bay Marine Education Centre, said there had been at least 300 jellyfish strewn across Island Bay Beach alone at high tide yesterday morning.
People should refrain from touching them and be cautious if they were planning to swim, he said.
"People need to be aware that even when they are washed up and dead, their tentacles can still sting."
Regional Public Health has also issued a warning against walking in areas where jellyfish have washed ashore, or swimming where jellyfish are visible.
Bluebottles are a common cause of jellyfish stings, and can kill if their tentacles are wrapped around the chest near vital organs.
Chef Al Brown said his daughter, Alice Longbrown, 12, had a red rash and swollen leg after being stung three times while swimming in Lyall Bay on Friday night.
A celebratory swim to mark the end of the school year turned into an excruciating experience when Alice hobbled from the water with marks from the jellyfish tentacles imprinted on her skin.
"She was bloody sore for an hour or two, but now it's more like, `Look where the jellyfish got me,"' Mr Brown said. "It's not putting any of the windsurfers off, though."
A woman reported being stung on the face while diving for scallops in the Matiu/Somes Island area.
Otago University marine biologist Miles Lamare said it was likely that warm conditions had allowed a population explosion among jellyfish on the east coast of the North Island and that currents and strong southerly winds had then blown the jellyfish off track.
"Its dispersion would normally be north of Wellington ... but the currents have come together to bring them into Cook Strait."
There is evidence to suggest jellyfish populations are increasing worldwide as predators are overfished.
He said the other species stranded on beaches appeared to be the mauve jellyfish, which were a "worldwide nuisance".
The stings are not fatal, but very painful.
"It's a bit like getting a lot of bees stinging you all at once, because the tentacles have got a lot of [stingers]," Mr Lamare said.
The bluebottle (physalia, pacific man-o'-war) is not a true jellyfish. It has a bright blue body, grows up to 15cm round, and has the potential to kill if its tentacles envelop vital organs. It is slightly different from the portuguese man-o'-war, which is bigger and deadlier.
The mauve stinger jellyfish, or pelagia nocticula, is a stinging jellyfish that often washes ashore in large numbers in Europe, closing beaches. It can kill large fish and has been known to wipe out salmon farms in Ireland, but it is not fatal to people.
- The Dominion Post
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