That is a good idea, truth be told, I have seen a fish have a heart attack, it jumped twice, made a brief run, and bacame completely limp on the end of the line, the guide propped up between a couple of rocks and left it there by law. I respected the guides decision. I did not like to see the grilse left for the predators. Unfortunately, one tag would get abused. How about a one tag , grilse only. Worldwide. Pay the higher fee, put the rest into research and enforcement.
A wet fish is a Happy fish