Working for dept. of fish and game being a tech. 11 we caught tagged and released  approx. 60 Lake Trout at the seven mile lake ice fishing. The mortality factor was 0, when we netted them in the summer. Use only cheap Eagle steel hooks, never stainless and cut the line if using live bait. I cannot say the same for Rainbow,s  and think at least 10% factor. Grayling are also a tough fish.