I think fish and all other animals have to feel Pain. It's a natural defense. If they couldn't feel pain, and their only goal was spawning, then why would they ever run downstream when hooked? The ability to feel pain is a necescity for survival, think if a fish was bitten by a seal and didn't feel any pain, odds are that every salmon that got close to a seal, or any other predator would be dead. I'm sure i'm not the only one who's seen salmon in the river with bite marks on them. A bit off the point, but i had a friend who cut his finger to the bone with a fillet knife, and couldn't feel anything past the cut. Being the bright person he is, he was stirring a pot of boiling water with his numb finger, and saying "look mom, it doesn't hurt at all."