The short answer: We don't know, exactly.
The longer answer: They almost definitely feel something, and there are innovative fishing companies and marine life activists working to help sea creatures get protections similar to those of land animals.
That might take a while, though. That's partly because we don't have a clear answer about what fish feel. It's always been difficult for scientists to determine what animals can and can't feel, since they can't tell us about it.
But it's even more complicated to figure out if fish feel pain, because they lack the brain structure that humans understand as the component to feeling pain, according to a new report in Smithsonian magazine.
Fish don't have a cortex, which is the highly complex part of the human brain that, among other duties, processes and churns out the different kinds of pain we might feel.
But no "cortex, no pain" is a bit too simplistic of an answer for some scientists. It could be that fish brain systems work differently than ours in processing pain, and several studies have indicated that some types of fish at the very least go out of their way to avoid situations that could be painful.
There's pushback on that idea, though, especially from seasoned fishermen. Why doesn't a fish squirm away when it's about to get its head chopped off? A dog would yelp and howl in a similar situation. Since fish don't, they must not feel it — or so the theory goes.
But we don't have any good science that proves that fish don't feel pain.
So marine activists are trying to get people to operate under the assumption that they do feel something — even if it's different from the human pain experience — and adjust fishing practices accordingly.
Norway and the U.K. have been at the forefront of humane fishing practices. Many fish farms there are opting to quickly knock out a fish with an electrical current or blow to the head. While the animal is unconscious, they get bled out.
Because of its speed, this method is considered more humane than other killing tactics, such as suffocation, ice chilling or carbon-dioxide poisoning. It marks a solid step forward in helping these fish go out with a little more dignity and a lot less (potential) pain.