Saiyan Knight Mk-II
Land animals are understandable food sources, though, because if we didn't eat them they would over-populate and muscle their way into a dominant stance over the food chain.
Only because we've bred millions upon millions of them.
If you'r argument applies to fish, it applies to ALL creatures.
Don't get me wrong, I hope that in the future we develop ways to easily gain all the nutrients we need and move away from the consumption of other animals.