None of them is approved for use in farmed seafood in the United States and some of them have been shown to cause cancer when fed to laboratory animals for `` prolonged periods of time , '' Acheson said . China blocks import of shrimp , catfish , crab , fish and dace from China . Fish ' n't be allowed until importers prove they are safe . The fish were treated with antibiotics and antifungal medication . The treatments are not effective in the fish .
China blocks import of shrimp , catfish , crab , fish and dace from China . Fish ' n't be allowed until importers prove they are safe . The fish were treated with antibiotics and antifungal medication . The treatments are not effective in the fish .