or hausen Large species of sturgeon (Huso huso, or Acipenser huso) that inhabits the Caspian and Black seas and the Sea of Azov. It reaches a length of 25 ft (7.5 m) and a weight of 2,900 lbs (1,300 kg), but its flesh and caviar are less valuable than those of smaller species. or white whale Species (Delphinapterus leucas) of whale found in the Arctic Ocean and adjacent seas, in both deep offshore and coastal waters. It may also enter rivers that empty into far northern seas. A toothed whale with a rounded forehead and no dorsal fin, the beluga is about 13 ft (4 m) long. Born dark blue-gray or blackish, it fades to white or cream at 4-5 years of age. It feeds on fish, cephalopods, and crustaceans and usually lives in groups of five to