we always place the fish on a stringer and let it trail behind the canoe. Never had we had the fish die. Of course we do this when fishing and not traveling a long distance with both paddlers digging to get there.  Then at camp we leave them on the stringer until its time to cook and the fish is fresh.

We don't portage fish either. I did once and then realized what a waste there are so many fish why would you carry it around?

The only problem we have ever had with this method is if left over night the Snappers will clean you stringer of all fish.