Bleed them? Wow, I just fillet them when I get home, regardless if they are alive or not. A lot of old wifes tales floating around this thread.
Not sure what you fish for, but if you fish for tuna, mackerals, kingfish or other similar saltwater fish you definitely need to bleed them. Cut the gills and place them head down in ice will do it pretty quickly. Otherwise the meat will be tainted. We make sushi and sashimi right on the boat and I can tell you if you don't bleed them they will taste like crap...
As far as humane? I have caught large saltwater fish with massive hooks hanging our of their mouths and big shark bites in thier backs and they are eating like there is nothing wrong, so I don't really believe that they feel pain anyway. Either way, if I am going to keep them I kill them right away and get them on ice.