I REMEMBER fondly summer holidays with my children at Southwold on the Suffolk coast when one of the regular highlights was taking part in the annual crabbing contest. We regularly used to lift out hundreds of crabs of various sizes by dangling old fishheads and bits of bacon rind into the water. Now, it seems, the crabs are trying to get their own back by invading my home waters.
The specific problem comes in the sizeable shape of the Chinese mitten crab – Latin name Eriocheir sinensis – which was first discovered in UK waters in 1935 and which has now been seen as far upriver as Staines and even Windsor.
The crab, which gets its name from the soft bristles which cover its substantial claws, is believed to have arrived in Europe in the ballast water of ships trading with China and the Far East in the early part of the 20th century. When that water is pumped out to be replaced by new cargo, the crabs and other creatures are pumped out with it and rapidly establish new colonies.
You would be forgiven for thinking that the arrival of a few foreign crabs might not be much to worry about but environmentalists and river watchers are growing increasingly concerned about the growth in the numbers of mitten crabs on the Thames.
One problem is that the animals – which can grow to the size of a dinner plate – are omnivorous, eating anything and everything that gets in their way including many native species of molluscs, fish eggs and freshwater crayfish. But aside from the effect they have on the native fauna, the mitten crabs love to burrow deep into the soft mud of unprotected river banks. When they do so in numbers they can very easily undermine the bank causing it to collapse. In the worst case scenario, that could present real problems for riverside properties.
The UK is not the only country to be worried by the invasion.
Dr Paul Clark from the Natural History Museum has been studying the creatures since he was sent to pick up a specimen found in the cooling water intake at Lots Road power station in Chelsea in 1976. He said: “Mitten crabs have been found in France, Germany and several Mediterranean countries. Indeed, in Holland, they have reached epidemic proportions with numbers in the millions,” he says.
So what’s the solution? Well in their native China, mitten crabs are considered something of a delicacy so perhaps we could just eat our way out of the problem. And according to Dr Clark, that’s precisely the answer the ingenious Dutch have come up with.
“They tried controlling them but it was a losing battle,” he said. “So now they’ve started to catch them and exploit them commercially. They’re even sending them back to China for consumption.” Perhaps there’s a commercial opportunity there for some enthusiastic entrepreneur on the Thames…
If anyone in the Leader area has seen one of these creatures while out walking along the banks of the Thames, I’d be interested to hear about it.