I put them in ice water (small bag of ice + gallon of water) when we transfer from the live well to the cooler . It stuns them, maybe kills them (we've been over this on this forum before) but at any rate, they have the appearance of death. This works better in summer than in cooler weather.
A way to quickly bleed out a fish it to cut the flesh under the gill plates that connects the underside to the lower jaw. That's how I kill the trout I intend to clean since I leave trout whole.
A quick plunge of a knife right behind the gillplates at the midline will usually hit the artery coming from the heart , but that will fill the body cavity with blood. - Roberta