Simon Walker's picture

Freshwater Mussel, Grafham Water, 2013-02-04 001

Observed: 9th February 2013 By: Simon WalkerSimon Walker’s reputation in InvertebratesSimon Walker’s reputation in InvertebratesSimon Walker’s reputation in InvertebratesSimon Walker’s reputation in Invertebrates
Freshwater Mussel, Grafham Water, 2013-02-04 001
Freshwater Mussel, Grafham Water, 2013-02-04 002
Teal, pair, and Freshwater Mussel, Grafham Water, 2013-02-04 001
Description:

This freshwater mussel was found on the edge of a ploughed field, about 100m from Grafham Reservoir. It was one of about half a dozen, all of which showed damage. All within reasonable proximity to each other - perhaps 10m.
But by what got them? Gulls? Crows? Either are plausible suspects. The water level is low, and there are lots of Black-headed Gulls and Carrion Crows about. I've certaily seen crows having a go at mussels; not so sure about the gulls. I suppose it could even have been a mammal, maybe a fox.
Interesting, though.
The third picture shows Teal feeding along the shore right next to another mussel shell.

Identifications
Species interactions

No interactions present.

Comments

Brian Cambridgeshire's picture

Probably Swan...

It's not always easy to tell Swan from Duck Mussel, A. anatina. The latter usually has a more wedge-shaped shell, and is never more than about 12cm long. A. cygnea has top and bottom edges nearly parallel and can reach 20cm. In the hand, the shell of Swan is quite thin, but about the same thickness all over, whereas Duck is uneven, thicker at one end than the other. Inside, the shape of the scar left by the adductor muscle is destinctive (but hard to describe or photograph!).

Two other potential suspects: mink will apparently take them, and I've been told of Brown Rat diving for them in the River Ouse in Bedfordshire. And it's not unknown for anglers to use them as bait.