I believe that happiness and boredom are words that we use to associate with certain bio-chemical & electrical processes that occur within our brains and bodies. It is leap to assume that fish experience anything similar simply because they seem less advanced than people.
Used to be that it was so clear than "non-human" species couldn't do or feel anything. I think that is increasingly hard to argue... take for example chimps using tools and language. Go back 15 years and you would have commonly heard. "Chimps aren't capable of language, they don't have developed enough brains..." I don't think that is a common opinion any more.
Didn't we already decide that fish "feel" pain?
...always easy to get me going!!