Panga is also known as basa.
I did read up on it a little bit and thought there was a bit of a conspiracy.
"In 2002, the United States accused Vietnam of dumping catfish, namely Pangasius bocourti and Pangasius hypophthalmus, on the American market, charging the Vietnamese importers, who are subsidized by Vietnam's government, of unfair competition.[6][7] With pressures from the U.S. catfish industry, the United States Congress passed a law in 2003 preventing the imported fish from being labelled as catfish, as well as imposing additional tariffs on the imported fish.[8] Under the U.S. Food and Drug Administration ruling, only species from the family Ictaluridae can be sold as true catfish.[9] As a result, the Vietnamese exporters of this fish now label their products sold in the U.S. as basa fish or bocourti.[10][11]
At the height of the "catfish war", U.S. catfish farmers and others were describing the imported catfish as an inferior product. However, Mississippi State University researchers found imported basa were preferred in a taste test 3-to-1.[12]"
http://en.wikipedia.org/wiki/Basa_fish