I've never seen a fish leave a cooler but have seen plenty rip off stringers or forget the stringer is on the side and go for a move.
Iced down is easiest and makes for easy fish accountability.

Would hate to try and put 45 or 50 catfish on
a stringer or in a basket, what a ordeal getting them off,
Happy Fishing Jerry R.

Here's a little more detail than you probably wanted. Fish have enzymes in their bodies just like we do, both digestive and metabolic enzymes. When you hook a fish, even before it is landed these metabolic enzymes go into overdrive. Once the fish is landed and begins to die, these digestive enzymes kick in and begin the process of decomposition. The warmer the temps, the fatser the decomp occurs and spoils the fresh taste of your fish.
Ice or ice-water slows this process down tremendously. If you want to go a step further, gut your fish as soon as they're caught and then ice them down.

I ice any and all fish I plan to eat, immediately. If I have time, I will gut them, too.

Fish handled in this manner will taste much better than a fish left to die at ambient temperature.

I also believe in bleeding my fish. Anything that I'm going to keep I cut and then throw in iced water. The rapid change in temperature with a cut gill will draw that blood (heat) out of the fish faster, leaving a whiter, better tasting fillet. IMOP

I just like to hear one flop around in my ice chest. They do clean easier and they tend to fin me less too when I take animation out of the equation. In the winter I'll just use a bucket if the temp will allow.

Not only are they easier to clean cold and immobile, especially for a skinner like me, but they don't bleed as much neither.

I've also seen people throw fish in the bottom of the boat in warm weather ... now that I've never understood. :(>

I insulated my front livewell

Ok..This may be a little off topic but it's sort of related. Has anyone heard of placing a fish on ice and then directly in the freezer when you get home. (not cleaning it) Then cleaning it whenever you bring it out to cook it. A older friend of mine does this. I told him it seems unhealthy and a 'lil nassy but he says that's the way he's done it all his life. Needless to say, I don't attend his fish frys.

I know some old folks who do this as well, I don't know if it is bad or not for the meat, but I know that the way I clean fish makes great fillets.

I wouldn't recommend it. Also if you place one whole fish and freeze it in a bag that would take up alot of room in your freezer, ecspecially if you had alot of cats. I don't like the idea of freezing it and thawing it with all of it's insides. Yes it does sound a 'lil nassy.

Just what I need. Reach in the Freezer for a popsicle and get finned by a stinkin catfish.

it's already been said but a dead catfish in 90 degree water will get soft and mushy so it's probably best to just throw them in the cooler so that the meat won't spoil on ya. when I'm out this time of year I try to keep them alive but I'll always have several die on me even if they're not hooked deep because the oxygen depletes rapidly in the livewell and if you dont' run the livewell constantly they'll croak ... best way to keep them fresh is to either throw them in the cooler with ice but I find that I don't have enough room to do that so I knock the fillets off of them as soon as they die and throw them in the cooler with skin on so that they're easily recognized if I get stopped by a game warden. drop those fish or fillets down in cold ice water and they're twenty times better than fillets off fish that have been dead in 90 degree water for a few hours.

when I quit fishing this time of year I'll get about two miles from the boat ramp and pull all the fish out of the livewell that have survived and cut their gills and put them back in the livewell and by the time i get to the ramp they're bled out and dead ... just takes a few minutes for them to die in the hot water but it takes about two hours for them to die in 38 degree water so in the winter I cut the gills just as soon as we catch um and throw them in the livewell ... that way they don't beat me to death when I get ready to clean them. in the cold water they'll stay fresh all day long.

catfish thrown in the bottom of your boat will also stay fresher than if you throw them in hot water in a livewell that's not circulating all the time. it'll take quite a while for the fish to die just laying in the bottom of your boat unless the air is really dry which isn't likely in the summer months ... during the summer when it's really humid their gills won't dry out very fast and they can actually breath out of the water a little better than they can in the oxygen depleated water in the livewell.

Yeah, that sounds like a good way to get a horrible case of the squirts!

I think that putting fish on ice makes it easier to clean them later. Easier to skin cats and clean crappie.

Plus 1 on this one, its not fishing without fishy smelling beer cans. lol

also Its just much easier to throw the fish in a cooler and not worry about it, I dont know how many times my catfish have done some serious water skiing across the lake heading back in because i forgot to pull in the stringer, lol.