I went down to Cove Brook to get some peace and quiet but nature thought otherwise! First it was nice to see a fish swim by, over a foot long with a wide round head, which I was very surprised to see in the Brook, likely a pike or maybe a cat fish. The foxes were all out and then one caught something down by the water, it was horrible, whatever it was, was screaming and screaming desperately for 10-15 minutes then went quiet, I saw the fox but it hid whatever it had caught. I thought I liked nature BUT...... I wonder if it was maybe a mallard or a moorhen, I'm also worried it could have had babies but the grass is long there, I couldn't get near enough to see. I must have seen 4 foxes there tonight, I do love foxes, my allotment foxes are really lovely, they mate for life and really look after each other and are a close pair, but I do wonder what it caught and I hope they don't eat all the ducks :-( Nature red in tooth and claw.
As you say, nature red in tooth and claw, or as often said, hunt and be hunted.
I can't help you with the fish ID, and certainly not without a photo, though someone might be able to. As for the foxes, there's a good chance they will have had a mallard, or two. Their cubs are now growing fast and many almost adult fox size, so will have the food requirement of an adult.
Mike
Flickr: Peak Rambler
There are large species of Carp in the UK and there are also wild Catfish which can grow very big...