Chinese Mitten Crabs

[Marineboy]

Hi there. There is a real threat to some of our British waterways, from an alien species - the Chinese Mitten Crab. Present in the River Thames, and various other locations, my nearest being watercourses in Devon, I was wondering if you all could let me know whether you have any further information on how far across the UK this species has got. Although for a crab fan like me it is news, but for our native fauna and waterways it is not so good. So what waterways near you have been invaded?

[JP]

Im just off he Thames in Essex, i live backing on to a river called the Mardyke and they infest the banks along it, some times they clear the banks with a JCB and this produces shed carapaces and bits of crab. Im off there tomorrow ill have another looksie

[Wild-Woman]

On the nbn gateway, there are only 4 sites. I should imagine it's a species that is vastly under-recorded because of their location in waterways and I should think a large percentage of the population wouldn't know what they look like. From what I have heard they are spreading quickly.

[Dan Salter]

Hi Marineboy.

As a self penned Nature nazi i have a keen interest in all things non native and invasive. But i honestly have not read up enough on Chinese mitten crabs yet to give you too much advice although a colleague in my uni class researched them for an assignment...he tells me they are a huge problem and spreading very fast..i believe they are in the thames /thames estuary which is my local patch...not sure if they are in our river medway though?...are they purely salt water/brackish or like the signal crayfish do they infect all waterways?

[Marineboy]

There are crab species throughout the world that will live equally happily in salt, brackish or fresh water. There is no reason why this species should not take a liking to our freshwater waterways. But is the breeding cycle of these crabs limited to marine conditions?

[Chiltern Chris]

I’m not sure of the UK distribution but I can probably find out next week. In the Thames river basin they infest all the tidal reaches including as JP said Mardyke, up the Roding (I think the Ingrebourne is free because of frog Island), the Lower Lee (around the Olympic site), and up the Thames as far as the Wey. On the Rhine they’ve marched 1000km upstream.

I’m not an expert on mittens but I think they can only breed in marine conditions and they go on mass migrations back to the estuaries at times.

The only good thing is that they appear to eat signal crayfish.

Chris

[Marineboy]

Is that with or without the marie rose sauce?

[Chiltern Chris]

Not sure about the sauce but I have seen them ready cooked in the hot discharge water from the power station on Chelsea creek in London! (that’s the power station that used to power the London underground).

[tom00_uk]

what devon waterways have them in? i would be keen to take a walk and try and see these guys

[Marineboy]

Hi Tom, and others,
Yes, we have them here in the south west. Check out these reports. First is from Glaucus, (another great site for those who might not know it - more to talk about here!)

British Marine Wildlife News 1998 (British Marine Life Study Society)

17 November 1998 - The alien Chinese Mitten Crab, Eriocheir sinensis, was discovered in the Teign estuary, Devon. This is a serious pest species and an investigation is underway. This crab has not been discovered on the English Channel coast before".

And another nice posting about Devon wildlife at - The story of the Mitten Crab