I'd be more concerned about eating those farm raised catfish and talapia from brazil, tialand, etc where they are raised in rivers just below cities where the effluent is fed to them, and that probably includes most catfish served in restaurants.
I don't know, but suspect most catfish consumed is farmed in the US.
As to farmed catfish, it's a pretty clean operation. I once watched lawyers argue for hours over a lawsuit where a guy sued one of the local catfish processors that refused to buy his fish because they didn't meet the taste standard. I work and live in the heart of catfish farm country...the area I work produces a huge number of cats for commercial sale. The processors are extremely picky about the fish they buy. In fact, farm raised cats are supposed to have virtually no taste. They're supposed to be a blank canvass upon which to season and create tastes you desire. That's the reason they're top fed, and why the soil make-up at the pond is so crucial.
