With a name like ‘mitten crab,’ you would be forgiven for assuming that this crustacean is a cute and harmless creature. It is causing chaos in the waterways of the UK and many other parts of the world. Now, the authorities are taking steps to try to control it. The unwelcome visitor is rapidly growing in numbers and they are hungry! The crabs have been filmed devouring sea snails and they also feast on salmon and trout eggs. These are both native UK fish species that are already under threat.
In an attempt to control the situation, scientists have created traps. They have a letter box construction and have been designed by engineers and scientists. The traps have two openings one faces upstream and one faces downstream. The hope is that the crabs will climb into the letter box and then up the pipes where they will get stuck. The project is being run in conjunction with Lincolnshire Wildlife Trust and the Welland and Deepings Internal Drainage Board.
What Exactly Are Mitten Crabs?
The scientific name for mitten crabs is Eriochier sinensis. They are a native species of eastern Asia but first appeared in Europe in the early twentieth century. They have also become established on the west coast of the US and have recently appeared on the east coast. The crabs likely arrived in the ballast water of ships. However, some could also have escaped from ethnic markets and aquariums.
It is not hard to spot a mitten crab because they have such an unusual appearance. These crabs are a gray-green or dark brown color and are about the size of an average dinner plate. They have white-tipped claws. However, their stand-out feature is their ‘mittens’. Their front claws are covered in a thick coat of brown fur!
Why Are Mitten Crabs a Problem?
UK salmon populations are damaged by mitten crabs.
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As is the case with many invasive species, mitten crabs are damaging the delicate ecosystems that they have invaded. They can also cause a decline in natural vegetation. In the US and the UK, they are damaging stream banks and their huge appetites are threatening local fish populations. This is one of the few invasive species that can impact both freshwater and marine ecosystems. This is because their life cycle involves both rivers and the sea.
How You Can Help Control Mitten Crabs
In the UK, you can help by reporting sightings of this crab. You can do this on an online form via the Natural History Museum website. The site also gives plenty of information about how to identify the crabs correctly.
