Yes! They will eat live fish.
I gave my chickens a live fish supplement from 8 weeks to about the time they started to lay.
Small pond, minnow trap, compressed slice of white bread. I would catch 25 to 50 minnows every morning, take the minnows and dump them onto the floor of the tractor. 30 seconds minnows gone, chickens looking for more.
Minnows were about the size of my little finger. Not a burp, slurp or anything, they would just gobble'em down.
I would not present the fish to my chickens in a bowl of water, I would just chunk the fish right into the run.