Sturgeon

Sturgeon Temporal range: Cenomanian–Recent PreꞒ Ꞓ O S D C P T J K Pg N
Atlantic sturgeon (Acipenser oxyrinchus)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Acipenseriformes
Family:	Acipenseridae Bonaparte, 1831
Genera
Acipenser Sinosturio Huso Scaphirhynchus Pseudoscaphirhynchus Fossil genera: †Boreiosturion †Protoscaphirhynchus †Engdahlichthys †Anchiacipenser †Priscosturion

Sturgeon (from Old English styrġa ultimately from Proto-Indo-European *str̥(Hx)yón-^[1]) is the common name for the 27 species of fish belonging to the family Acipenseridae. The earliest sturgeon fossils date to the Late Cretaceous, and are descended from other, earlier acipenseriform fish, which date back to the Early Jurassic period, some 174 to 201 million years ago. They are one of two living families of the Acipenseriformes alongside paddlefish (Polyodontidae). The family is grouped into five genera: Acipenser, Huso, Scaphirhynchus, Sinosturio, and Pseudoscaphirhynchus.^[2][3] Two species (H. naccarii and S. dabryanus) may be extinct in the wild, and one (P. fedtschenkoi) may be entirely extinct.^[4] Sturgeons are native to subtropical, temperate and sub-Arctic rivers, lakes and coastlines of Eurasia and North America.^[5] A Maastrichtian-age fossil found in Morocco shows that they also once lived in northern Africa during the Cretaceous.^[6]

Sturgeons are long-lived, late-maturing fishes with distinctive characteristics, such as a heterocercal caudal fin similar to those of sharks, and an elongated, spindle-like body that is smooth-skinned, scaleless, and armored with five lateral rows of bony plates called scutes. Several species can grow quite large, typically ranging 2–3.5 m (7–12 ft) in length. The largest sturgeon on record was a beluga female captured in the Volga Delta in 1827, measuring 7.2 m (23 ft 7 in) long and weighing 1,571 kg (3,463 lb). Most sturgeons are anadromous bottom-feeders, migrating upstream to spawn but spending most of their lives feeding in river deltas and estuaries. Some species inhabit freshwater environments exclusively, while others primarily inhabit marine environments near coastal areas, and are known to venture into open ocean.

Several species of sturgeon are harvested for their roe, which is processed into the luxury food caviar. This has led to serious overexploitation, which combined with other conservation threats, has brought most of the species to critically endangered status, at the edge of extinction.