I also don't believe fish feel pain (at least not in their mouth). If they did, they would only eat soft things not spiny fish or crustaceans. Imagine putting a spiny perch in your mouth and chomping down on a dorsal fin, or a catfish and getting one of those spines in the roof of your mouth...you would never eat a perch or a catfish again. And of course we know that doesn't happen. I believe fish fight because they are being pulled in a direction against their will, not because of pain. If you stop pulling the fish stops fighting. Seen lots of fish just sit quietly in one spot if you stop reeling.