If they are hooked inside the mouth, I just cut them loose as close as I can get without taking them out of the water. If they are hooked outside the mouth I just grab them by the nose and turn them upside down. It has a paralyzing effect on them and you can simply take your time and unhook with a set of pliers.
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In the legend of King Arthur, the Fisher King was a renowned angler whose errant ways caused him to be struck dumb in the presence of the sacred chalice. I am no great fisherman, and a steelhead is not the covenant of Christ, but with each of these fish I am rendered speechless.