This is a question commonly asked by those new to fishing. And it’s a good question, too; many otherwise experienced anglers don’t know the answer. Actually, it’s difficult to prove scientifically whether a fish feels the sting of a hook in its mouth the same way that I would feel that same hook in my mouth (that has never happened to me, although a friend of mine once hooked himself in the nose while flyfishing on a very windy day, and he said it hurt quite a bit). We do know that fish respond to being hooked: They fight and leap and bull toward the bottom, always putting pressure against the angler’s fishing line (never in my life have I hooked a fish that came directly to my hand or net). But that still does not signify pain as we know it. As a matter of fact, fish exhibit some traits from which we can construe that they don’t feel pain at all. For instance, many times I have had a fish on my line including bass, pickerel, bluegills, and numerous saltwater species that I lost moments after I hooked it. These fish had the point of the hook embedded far enough into their mouths to respond to it by fighting. For whatever reason I didn’t set the hook hard enough, the hook point itself was dull, I didn’t keep a tight enough line the fish was able to dislodge the hook from its mouth (throwing or spitting the hook, as it is commonly referred to). Yet on one of my next few casts, I would hook the very same fish. When I was young, sometimes I would lie down on a small boat dock and fish for the little bluegills and pumpkin seeds that took refuge in the shade of the structure. I would dangle a worm-baited hook just a foot or so under the surface and watch the panfish come out from the shade, observing the worm. Eventually one of them would dart over and try to grab the worm try, because often the mouths on those diminutive bluegills would be too small to engulf the whole worm. So it would become a matter of striking exactly when just the point of the hook was positioned at, or just inside of, the fish’s mouth. So many times I would have a bluegill on the hook for a matter of seconds,watching while it tugged against the line and tried to swim back to the safety of the dock’s shadow, and then it would throw the hook. I’d reel in, rebait with a fresh worm, drop it back in the same place, and witness that same bluegill come out, study the worm, and try to eat it again. Similarly, I have fished lakes for bass with a top water lure (which imitates a frog or a mouse or a wounded bait fish) and had a bass jump up, grab the lure, and start swimming away. Now, many surface lures are made of hard plastic and feel very much unlike a frog, not to mention the shiny and sharply honed hooks dangling from them. The bass would shake its head, losing the hook, and then come back to hit it again.
Also, many people have witnessed sharks in a feeding frenzy that are so keyed into eating that one shark will occasionally take a bite out of another. That wounded shark would then as gruesome as it may sound turn and actually begin feeding on itself. Some people may argue that fish do feel pain; the reason that they don’t react to it is that their sense of hunger the predatory instinct is much stronger than their sense of pain. But I’ve also fished enough times when, for whatever reason, the fish just won’t eat anything, to disallow that reasoning. My personal, unscientific theory is that fish do feel something when they’re hooked, but it is not at all the same sensation that humans would experience. In other words, it doesn’t hurt them