The Loch Ken monster

The Craywatch project focuses on North America (for now), but other countries provide good examples of why we need to keep an eye on crayfish.


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This news article tells of the economic costs of invasive signal crayfish (Pacifastacus leniusculus) in Loch Ken, Scotland (emphasis added):

Susan O’Hare, who runs the Cross Keys Hotel in the town, said: “We have had fishermen who came last year who are now booking trips in Ireland. We can lose between £3,000 and £4,000 a weekend. My fishermen have been catching crayfish after crayfish.”

One million of the creatures were removed from the loch by a cull carried out in 2009.

Just a few weeks before that, another report from Scotland described a new fence that had been put in place to try to contain the signal crayfish:

"Unfortunately there are no techniques available that will allow us to get rid of signal crayfish from rivers and streams," said Dr Colin Bean, a freshwater adviser with SNH.

"So taking the radical step of developing and installing a physical barrier may offer us the best hope of stopping the species from moving into new catchments."

Two dams have now been installed 20 metres apart at a cost of £50,000.

I wish them luck. But the Australian experience with fences suggests that invaders are very good at getting past them. It’s not clear to me how fences will stop little larval crayfish.

And finally, this story isn’t so much about the economic cost, but the loss of biodiversity and native heritage:

More than 50 dead white clawed crayfish were found in Chad Brook, Long Melford.

The Environment Agency confirmed the deaths were caused by the disease, rather than pollution, and it expects the rest of the colony to perish. ...

Only two colonies of native crayfish remain in the East of England in their natural setting.

Keep watching the streams!

Crayfish picture by shimgray on Flickr; used under a Creative Commons license.