I keep the smaller ones alive on the gameclip, gaffing doesnt kill them right away, takes sometimes a couple hours. all they do is swim around a little. and its buy you time on a hot bite.
If you leave them dead to long, The worms crawl out of the stomach and into the good meat.
If you get a Big one I'd imagine pop a kill and paddle back in. let them swim aroudn a minute while your getting everythign resituated. they will still be plenty alive byt he time you land, then weigh it, gut it then throw it on ice.
Never had any worms in any of my halibut.
Nice Fish!