Good Morning ummmm,
I've been around salt and fresh water all my life, and as long as I can remember (starting around the time Moby Dick was a minnow), there has been this theory that "sea creatures, fish in particular, 'Don't feel pain'."
I've never understood how these people, nor could they explain in a way that convinced me, how were they so sure?
Therefore, I treat them in the same manner as I would a land creature. If they are to provide sustenance for my family, I ensure that they are humanely reared or hunted, and they are not allowed to suffer unnecessarily.
But, in answer to your question, it is my firm belief that they must be able to feel pain; any living being must suffer when wounded. My Dad and Grandfather and everyone else I grew up with, always expertly despatched land and sea creatures as quickly as possible.
Sorry to go on a bit, only excuse is I tend to ramble-on as I get 'real old', but at least I don't drool.................yet.
Old Salt