Just when you thought it was safe to go back in the water ....
First there was a shark attack. Now, a plague of crabs has washed up on a Cornish beach
CORNWALL was left reeling this week from its worst shark attack in decades, after a snorkeller was bitten off the Penzance coast.
Just days later, when holidaymakers thought it was finally safe to go back in the water, a plague of poisonous crabs swept in on the tide.
The giant mass of spider crabs gathered in the shallow water off St Ives to shed their skins, creating a carpet of the spiky, ten-limbed creatures.
However, swimmers brave enough to risk a sharp nip from one of the crabs or a sore foot from standing on them should not be overly concerned.
The crustaceans may have a venomous bite to see off predators, but are actually harmless to humans.
In fact, there is a significant commercial fishery of the crabs, whose meat is popular in Europe.
Despite the crabs’ docile nature, more than a few visitors to Porthgwidden Beach were put off entering the sea by the gathering of the barbed decapods just below the surface.
A few brave souls, however, did dare to snorkel above them.
Kate Lowe, a marine photographer, captured the event with her camera.
“I go snorkelling most of the time throughout the year but I have never seen spider crabs in such numbers,” Ms Lowe said.
“When we turned up at the beach it looked as though there were lots of dark rocks under the surface.
“But it turned out that there were thousands of crabs just two or three steps into the water.
“It was just really incredible, they were only knee deep. I was able to float on the water above them and tried not to step on them.
“A lot of the tourists were squealing at the sight of them.”
The crabs gather en masse to help protect themselves from predators while they wait for their new exoskeletons to thicken and toughen.
While they have been seen in British waters in fewer numbers, mass gatherings like this are becoming more common in the summer owing to rising sea temperatures from climate change. The crabs are migratory and once their new shells are tough enough, they will disperse and disappear to depths of up to 300ft, leaving Cornish beaches quiet and claw-free.
European spider crabs are much smaller than their giant Japanese cousins, with their carapace reaching about 8in in width and a claw-to-claw measurement of 20in.
The crustaceans are common in the Mediterranean Sea and can migrate up to 100 miles over the course of eight months.
There were also reports that the spider crabs were spreading as far north as Norfolk, which is usually well outside their traditional range.
Fishermen in the seaside town of Cromer said they had caught dozens of the species where previously they had seen none.
“We don’t want to see spider crabs, because we’re fishing for brown crabs,” said Henry Randall, a crab fisherman in Cromer.
“Are we going to see more and more every year?
“Are they going to take over? That’s the concern.”
Scientists were quick to quell the fears, however.
Alastair Grant, professor of ecology at the University of East Anglia’s School of Environmental Sciences, said they were likely to “coexist with our more familiar Norfolk species, just as they do in south-west England”.
That sentiment was backed up by Ron Jessop, senior marine science officer at the East
‘I was able to float above them and tried not to step on them. A lot of the tourists were squealing at the sight’
ern Inshore Fisheries and Conservation Authority, in King’s Lynn, who said: “Normally, spider crabs won’t out-compete brown crabs.
“Spider crabs are slow moving, less robust and less aggressive than brown crabs.”
The crabs are not the first plague to strike the Cornish shores this summer. On July 28, a snorkeller was bitten on the leg, by what was claimed to be a blue shark, during an organised swim off Penzance. The company behind the tour said such incidents were “extremely rare”.
Last month, the local Wildlife Trust reported hundreds of octopuses swarming the county’s seas and devouring lobsters. Fishermen in the area have been able to sell the octopus meat to Europe, where it is popular, to make up for their lost crustaceans.