Fish-Eating-Vegetarians

It's surprising to me how many 'vegetarians' I meet still eat fish. It's a very interesting physcological question on what and who we extend our compassion to.

How come the morals and reasons that have convinced someone not to eat meat do not apply to fish? Is it because we are constantly told how good and essential fish is to our diet? Or is it because most fish are caught from the wild and so the factory farming issue doesn't apply?

Or is it because humans can't identify emotions or feelings from fish like we can from cows or pigs?

I usually contend that our moral compass as a society continues to grow but it starts from large animals down to the small (seriously... ask a mouse or a spider). I've heard the arguments as to why humans have a right to rule over and consume animals and when the arguments are defeated it is usually through examples of larger animals (many animals exhibit cognitive dissonance, empathy, grief). People can visably see a gorilla holding the body of their dead baby or an elephant funeral) but it's more difficult to visualize these traits in our marine life.

I'm not saying that all animals have the same level emotional intelligence or foresight but it's getting harder and hard to ignore the science that all animals feel pain in the same sense that we do.

You can find an interesting on how fish feel pain here.