As Norman says : minimize exposure to the air. Take a quick shot.
Watched a guy spend 20 minutes landing a 5 lb. trout one day. Then netted it & while it flopped around on the bottom of his boat he looked for something. Then he finally found the something and played with some fish some more. Got out his camera and took shot after shot. Then carefully lowered the fish into the water and say's to one and all. "It's dead".
What a surprise.
I frankly don't much care whether or not you believe what a published scientist has proved true. The reality is - time out of water kills fish with "grip and grin" camera shot being a major contributor.
If you want fish to fish for, take care of them.
And yes, I do take pictures of fish.
