I found this large freshwater mussel in my local canal yesterday (March 25th) whilst pond dipping. It's alive and was returned to the canal. I've never seen one this big in the UK. Can anyone ID it and tell me if it's a native species or an introduced one?
At this size it probably isAnodonta cygnea .... but other Anodonta spp. should be considered (A. anatina & A. complanata). Critical id requires looking at the umbonal ridges found on the inside surface of the shell - among others.
It's a whopper for sure, but not as big as we've had - see this posting from 2010 (good to see Lewis is still with us )