Between this bridge bridge at Hall Lane on the side of the canal are a lot of swan musscle shells, patches of them for good 250 yards...otters I wonder

Those swan mussel shells are left by men fishing on the canal - I used to think it was water rodents or something like that, but was told by a local fisherman that they use them for bait.

Yes I've seen these too a couple of years ago. There are many thousands of them. It is inconceivable that anglers coultake these from the canal in such numbers, break them open and put them on a hook!
Can only be otters.