I definitely wouldn't rule out river otters. Here in south central Oklahoma, I have seen them kill fish, eat a few bites and go kill another fish! No lie. It's like they are four legged serial killers. They just do it for fun! They can be nocturnal too. They are excellent swimmers and can stay down under water for quite a long time. I never realized they could be such a problem until I saw them first hand. Respond well to lead poisoning, but hard to see/find!
Eddie
