I know I wouldn't want my head held underwater for 10-seconds immediately after doing anything vigorous/strenuous, let alone 30-seconds or an entire minute!! No one should be surprised by this direct relationship between mortality and being removed from their source of oxygen after the stress and exertion of being played out. I'd offer folks shouldn't just reconsider the hero shot for steelhead but also netting salmon and bringing them onboard (i.e. out of water) if they don't intend to dispatch that fish - gaff in the bend of the hook, twist, yank and gone should be the norm for C&R on the chuck!!
Ukee