Fresh Water mussels.

[Clan Chief]

I was of the understanding that these were very rare. There were plenty of them all empty mind ye at a  loch I was fishing. I also thought they were to be found at running water. This was not the case.

[Wildfisher]

you get them on lochs too. I saw them many years ago on Rescobie loch (a large stockie bashing dub)

[bushy palmer]

Loch Fitty in Fife had them years ago too

[Clan Chief]

Thank you for your info Breac Uaig. Thought these ones might be common as there were dozens of them in the Loch.