Dead catfish with a stick in it's mouth, brings back memories. When I was a kid I went fishing and the kid I was with caught a catfish, and he decided it would be cool to put in a hated neighbors mailbox. I told him he was an idiot and I would have nothing to do with it. He did it anyway. What a moron.
Anyway, I hope your cat made to your pond by egg or mistake, and died of natural causes...