The beluga / b ə ˈ l uː ɡ ə /, also known as the beluga sturgeon or great sturgeon (Huso huso), is a species of anadromous fish in the sturgeon family (Acipenseridae) of order Acipenseriformes.It is found primarily in the Caspian and Black Sea basins, and formerly in the Adriatic Sea.Based on maximum size, it is the third-most-massive living species of bony fish.