I can't eat pig knowing how intelligent they are.
The only thing I really put in that category is octopus.

environmental problems with fish farming
It depends how they do it, and to a large degree on the fish. A few places have started experimenting with inland salmon farming, which avoids the problems of disease from overcrowded farmed fish getting into the wild population (but not that the salmon is still fed wild fish -- or that salmon taste like hell, for that matter). Farm-raised tilapia and catfish can be fed mostly plant diets, so they don't have nearly as much impact as carnivorous fish.