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Beachgoers are being warned to steer clear of a "false jellyfish" that washed up today on the Anglesey coast. A potentially deadly Portuguese Man o' War was found by swimmers on Porth Trecastell beach on Tuesday, September 16.
Coastguards have urged visitors not to touch the sea creature, regarded as a "fearsome predator" for it poisonous and "extremely painful" sting. Dogs should also be kept well away, even when the creature had died.
The stings are strong enough to kill fish and in very rare cases they have been known to kill humans. Rhosneigr Coastguard Rescue Team (CRT) said: "If stung, severe or lasting pain warrants immediate medical attention." All sightings should be reported to the Coastguard, it added.
Porth Trecastell (Cable Bay) lies between the villages of Rhosneigr and Aberffraw. A small beach in a sheltered inlet facing out to the Irish Sea, it's popular with families as it has gently sloping sand.
Portuguese Man o' War - also known as "bluebottles" - are not true jellyfish but siphonophores, made up of specialised colonies of individual organisms working together, rather than a single animal like jellyfish.
They are carried to UK shores by warmer Atlantic currents, particularly after storms - one was also found on Shell Island near Llanbedr, Gwynedd, last week. Sign up now for the latest news on the North Wales Live Whatsapp community
Typically they arrive in September and October as sea temperatures peak. Like jellyfish, they are indicators of Britain's warming seas as the climate changes. In its most recent Wildlife Sightings UK report, the Marine Conservation Society (MCS) said 280 man o' war were identified in 2024, a fourfold increase on the previous year.
As oceans continue to warm, experts predict increasing numbers of exotics on the Welsh coast in the years to come. Frankie Habro, owner of Anglesey Sea Zoo, expects specimens to get larger and, in the case of Portuguese Man o' War, pose bigger risks.
Already the creatures have been causing problems in the Mediterranean this summer. In July their presence prompted swimming bans on several popular beaches in south-west France.
In the Basque Country in Spain, yellow "jellyfish" flags were flown in early August and, in some places, swimming was prohibited. In one week alone, 36 swimmers were stung in the region.
People who come into contact with the creatures' 10-metre-long tentacles should not scratch or rub the injury. The affected area should be cleaned with seawater, never fresh water.
Debris should be removed with tweezers, or scraped out by a bank card - not with your hand unless wearing gloves. Sign up for the North Wales Live newsletter sent twice daily to your inbox
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