The Acipenseriformes or sturgeons and Paddlefish are large sized, late maturing ray-finned fishes (Actinopterygii) with an average life span ranging from 12 - 80 years, depending on species; some individuals of the larger species may live 140 years or more.
The order consists of two extant families, Acipenseridae with five genera and 26 species; and Polyodontidae with one genus and two species. The family includes anadromous and freshwater species of circumpolar distribution in the northern hemisphere (USA, Canada, Europe, Siberia, the Caspian Black and Azov Seas, China and Japan).
They are adapted to live in the large lakes, and extensive river systems that provide the diverse habitat they require for all or part of their life history. Although many species are adapted to live in marine environments along the coast, all spawn in freshwater. The Caspian Sea, with an area of 400, 000 km2, is the largest inland salt-water body in the world, and home to the greatest variety and number of sturgeons in a single water body, with 6 species. Many species undergo spawning migrations and other movements that take them across international borders.
These characteristics make sturgeon vulnerable to the impacts of human activities, especially capture for caviar and meat, as well as habitat loss and degradation from damming of rivers and pollution. Historically, exploitation and fishing (including poaching) have caused drastic declines in targeted species, however many species are also indirectly impacted as bycatch in fisheries for other fish species.