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Tourists warned as thousands of spider crabs litter shallow spots on Cornwall beach

Written by Javed Iqbal

A popular tourist destination in Cornwall has been overrun by a startling swarm of venomous spiders crabs.

Pictures shared on social media have captured the swarming crustaceans congregating in the shallows at Porthgwidden Beach, St Ives.

The crabs are there to shed their shells before returning to their breeding grounds as part of the species’ annual migration pattern to seek warmer waters.

When the crabs molt, they emerge through the back of their shell, leaving behind the entire exoskeleton including the legs and eyestalks, which may resemble an intact crab.

A snorkeler who dived down to catch a glimpse of the spectacle said she had never seen spider crabs gather in such numbers.

Kate Lowe, a marine photographer who snorkels at Porthgwidden all year round, said: “I snorkel most of the time throughout the year but I have never seen spider crabs in such numbers.

“When we showed up at the beach, it looked like there were lots of dark rocks under the surface. But it turned out that there were thousands of crabs just two or three steps down into the water.”

She added: “It was just really incredible. They were only knee deep. I was able to float on top of them and try not to step on them.

“Many of the tourists squealed at the sight of them.”

Mass gathering is thought to help the crabs protect themselves from predators while they wait for their new exoskeletons to thicken and harden.

The crustaceans have a poisonous bite that can kill their predators – but is harmless to humans.

Despite the reported boom in spider crab numbers in British waters, there is little market in the UK for spider crab meat, despite it being considered a delicacy in European countries including Spain and France.

But National Coastwatch St Ives told Cornwall Live: “They are just the shells of a crab, they are not dead.

“Those traps are shelling for new ones.”

Last July, a congregation of spider crab carcasses washed up on beaches at Anglesey off North Wales.

Photographs similar to those from Cornwall today captured the horrific tableau where the legs, claws and carapaces of washed-up spider crabs had piled up.

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Javed Iqbal

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