I had a warden actually hold a flashlight and help me land a fish that was hooked in daylight and I was unable to land until after dark. The fish wrapped itelf in a log jamb so he held the light, waded with me and after landing the fish, he snaps off his light, congradulated me on a nice fight and told me to remember to punch my card. This effectively left me standing in the river, up to my waist, in the dark blinded, gilling a struggling fish. I was kind of caught in a daze, the post adrenaline rush after worrying that he was planning on writing me up eventhough the fish had been fairly hooked. I would guess the situation may have ended differently with another warden. Who knows?
To answer the first question though-
I would not cast above a boundary line, but if a fish hooked fairly ran above the line I would fight from below the boundary and take my chances.
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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.