Fish survive for 15+ minutes out of water. Most of the bycatch will survive or be used for bait/food. The small amount of dead fish will be put back into the ocean and other animals will thrive off of it.
I'm a firm believer in fish excluders. I know there's a hole in the webbing, but I did a few experiments with open fish excluder on 1 net, and a closed fish excluder on the other net. The only difference was the net with the open excluder was cleaner than the other side. Both nets caught the same amount of shrimp.