Nevermind the expense, or the eutrophication of the immediate area. Hatcheries in the open ocean could have escapees, effectively peeing in the gene pool. I would explain, but I think this NMFS memo says it better:
http://www.nwfsc.noaa.gov/publicatio...30/leider.html. We should work on conserving our wild fish stocks instead of relying on technology to fix the results of our misuse of resources.