Eric wrote:

Harry

I had this problem last year. It sounds exactly like my garden and pond!

Keeping herons out of a pond is one problem but how the blazes do you keep
out grass snakes, I would like to know?

My little 'friend' was about the same size as yours and he had many of my
best fish during several weeks of the summer. I had always believed that
they swallowed them whole, but not a bit of it. I caught him eating the best
flesh off a lovely great fish, on the garden path, one day, and found
several more similarly killed in the bushes around the pond, later.

I suggest that if you actually saw the snake with a partially eaten fish,
it was eating something that had already been killed and partly eaten by
something else. You were right. Snakes swallow their food whole. They are
not capable of biting off bits. The snake is not to blame for the
dismembered fish you found.

Personally I'd rather have the snake than the fish but each to his own. I'm
glad you are merely transporting the offender rather than killing it.

Anita