I fish regularly on my pond and often mark my fish when caught - my unscientific survey is in line with Shan - I don't see any signs of bass dying that I have caught. My guess would be the vast majority survive if handled properly - Cecil is correct in the treble hooks and their damage - barbless hooks are also helpful and reduce damage. The biggest threat I see is fishermen who use live bait which adds to the number of deeply swallowed hooks. They will also swallow plastic worm hooks but if the hook is left in the gullet, they typically survive just fine. Just using common sense in handling them is the best approach.