The Aliens are here

I managed to get out today having been sofa-bound yesterday - knee still playing up. We drove to town, rather than walk as we usually do, to meet three generations of the Montague family, John, Hannah and baby Joel, in Welland Park. Just after leaving the café Hannah spotted this in the river. The River Welland is very shallow here and runs over a stony bed. I believe this is a Signal Crayfish - the one that, sadly, is bad news for our native white-clawed crayfish. We estimated it to be 7 or 8 inches long. It's the certainly the first time I've seen one. We do have other non-native crayfish, I think, but this one looks like the pictures I have since googled of the Signal variety