A 15-kilo fish with a flat body, short tail, and round head was caught by a fisherman off the central province of Nghe An.
Ho Van Doan, who caught the fish, said he froze it after it died one hour after being taken ashore.
Some elders in Quynh Luu commune where Doan lives have claimed that the fish is classified as a sunfish, or a Mola Mola, that rarely appears in the country’s sea waters.
The fish will be handed over to the Vietnam National Museum of Nature for preservation.
The Mola Mola is native to tropical and temperate waters around the globe. In Vietnam, the fish is listed in the Red Book of species that need strict protection.