The correct answer is "Dumping."
The U.S. catfish industry petitioned the U.S. government for increased taxes on imported Vietnamese fish, claiming that the fish were being sold below the cost of production. The U.S. catfish industry was accusing the Vietnamese fish industry of dumping.
Dumping is an international trade concept that refers to a country that exports a product at a lower price in the foreign market that imports it, than the price in the market that export is. This is considered a disloyal practice because the country that exports the product want to create a competitive advantage for its products.