Not in some cultures. My youngest daughter isn't a big meat eater, and certainly hates seafood. She was on an organised tour to Spain with her youth orchestra so ticked the "vegetarian" box for meals. Inevitably her meal came with fish as the protein. Apparently in Spain, fish aren't considered as sentient like chicken or hoofed animals and hence are akin to vegetables.

Which is not just lacking scientific basis but goes straight _against_ what we know today of fish.

Any vegetarian who eats fish because of that reason really needs to update their ethics to the current millennium.

It’s a Christian thing.