The Memo: Invasive species: First traps set for Chinese mitten crabs in the UK

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Invasive species: First traps set for Chinese mitten crabs in the UK

Emily Dunham – 23 October 2023

If you’re not familiar, the term ‘invasive species’ is used to describe non-native flora and fauna that is artificially introduced to a country, only to wreak havoc on indigenous wildlife. One example you’ll definitely be familiar with (even if it comes as something of a surprise) is the grey squirrel, but you probably won’t be familiar with the Chinese mitten crab – the latest non-native species to make its mark. With furry claws and ability to grow to the size of a dinner plate, you’d be forgiven for thinking that this crab sounds cuddly, but the species can be quite aggressive, and has been listed as an invasive species under the Wildlife and Countryside Act 1981 in the UK since August 2016.

The classification isn’t unwarranted either, the crabs disrupt the biodiversity of UK waterways (an ecosystem that is already under immense pressure) and compromise the stability of riverbanks as they burrow into them – how shellfish! The species is native to South East Asia, and was considered to be established in the Thames in 1973. But it has now been seen in waterways across the UK, and even shocked some dog walkers at a park in the Nene Valley in Peterborough!

Now, a group of scientists have been given special permission by the Environment Agency to test a trap for the crabs at Pode Hole in Lincolnshire. The project, which sees collaboration between the Lincolnshire Wildlife Trust, the Wellings and Deepings Internal Drainage Board and the National History Museum, aims to prevent the crabs migrating to breeding grounds to slow their spread. The site has been chosen because the village lies at the confluence of several drainage channels and has been reported to have a particular problem with the crabs.

There are some really complicated rules and regulations that cover this kind of thing, so it’s unlikely to be solved by a snappy decision. The Invasive Alien Species (Enforcement and Permitting) Order 2019 is a key piece of legislation here, and details when permits or licenses are required. The government’s guidelines require permission before you are free to put traps in waterways, and you cannot take live animals away from the riverbank, so must instead humanely kill them where you caught them (though there are some exceptions if you have a permit to keep live animals for research or conservation). The group involved in this project have a license to set their trap, but it does have some conditions placed upon it – the crabs will be frozen to be used for further scientific analysis, and cannot be transported live. Interestingly enough, they plan to use the crabs to research their digestive system!