Sturgeon

sturgeon, (family Acipenseridae), any of about 29 species of fishes of the family Acipenseridae (subclass Chondrostei), native to temperate waters of the Northern Hemisphere. Most species live in the ocean and ascend rivers (possibly once in several years) to spawn in spring or summer; a few others are confined to fresh water. Several species provide caviar from eggs. Most species are considered to be critically endangered.

The sturgeons are related to the paddlefish (family Polyodontidae) in the order Acipenseriformes. Fossils of sturgeons first appear in rocks dating to the Middle Jurassic (about 174 million to 163.5 million years ago). It is thought that sturgeons evolved from an earlier group of fishes called the palaeonisciforms, which appeared at the end of the Silurian Period (about 419 million years ago). The genera Acipenser, Huso, Scaphirhynchus, and Pseudoscaphirhynchus contain living species of sturgeons.