It is best to cut the line on salmon in winter. And not to remove any part of that fish from the water, just have your sharp knife ready every time and when you get his head in the hole cut the line as close to the snout as possible.
The hook wounding is not from small thin rustable hooks left behind during ice fishing, they do very little if any damage at all in that respect.
The wounding is not always from careless release sometimes no matter how careful you are something rips or tears, smaller salmon are very delicate.