A fillet knife.

Anything is humman compared to what I see alot of saltwater fishermen do. They fillet them alive and there still jumping. Do what the canadians do. Hold them by the gill and on the tail and left there spin back to brake there back. It kills them instantly. I think thats better then drowing a fish in a bucket then the few unlucky survivers get fillet alive.

gotta luv it!!!!!! We're talking about a fish here.

I open the drain on my livewell when I load the boat on the trailer. Takes about 15 - 20 minutes to get to the house, plug the charger in and get a bucket to put the fish in. By then they are pretty much dead. If not, by the time I scale them, cut a filet off one side and cut the head off, that pretty well finishes them off. I only keep small bass, many are a little to big to fry whole but not big enough to completely filet so I cut only cut a filet off one side, leave the skin on, cut the ribs out and cook the other half with the back bone in it. Cutting the filet's off both sides waste too much meat.

I prefer to clean fish that are fully dead and been dead for several minutes, they don't bleed out as bad into the meat like a live fish or freshly killed fish does, giving you much whiter, cleaner looking meat.