Sturgeon, fish of the north temperate zone whose eggs are eaten as caviar. Sturgeon have a row of bony plates down the side of the body and sharklike tailfins; toothless, they suck their food (mostly crayfish) from the water bottom. Most of the 2 dozen or so species are marine but breed in fresh water. The largest is the Russian sturgeon, or belluga (Acipenser huso), which grows to 13 ft (4 m) and can weigh 2,000 lb (908 kg). This species, which lives entirely in fresh water, provides half the world's caviar. The white sturgeon of the U.S. Pacific Northwest has been overfished and is now much reduced in number.