Biology and conservation of sturgeon and paddlefish

The Acipenseriformes (sturgeon and paddlefish)live in the Northern Hemisphere; half of thesespecies live in Europe, mostly in thePonto-Caspian region, one third in NorthAmerica, and the rest in East Asia and Siberia.They reproduce in freshwater and most of themmigrate to the sea, either living in brackishwater (Caspian, Azov, Black and Baltic Seas) orin full seawater on the oceanic continentalshelf. Most species feed on benthic organisms.Puberty usually occurs late in life (5–30 yearsof age) and adult males and females do notspawn on an annual basis. Adults continue togrow and some species such as the beluga (Huso huso) have reached 100 years of age andmore than 1,000 kg weight. Stocks of sturgeonsare dramatically decreasing, particularly inEurasia; the world sturgeon catch was nearly28,000 t in 1982 and less than 2,000 t by 1999.This decline resulted from overfishing andenvironmental degradation such as: accumulationof pollutants in sediments, damming of rivers,and restricting water flows, which becomeunfavorable to migration and reproduction.Several protective measures have beeninstituted; for example, fishing regulation,habitat restoration, juvenile stocking, and theCITES listing of all sturgeon productsincluding caviar. In addition, sturgeon farmingpresently yields more than 2,000 t per year(equivalent to wild sturgeon landings) andabout 15 t of caviar. Hopefully, thisartificial production will contribute to areduction of fishing pressure and lead to therehabilitation of wild stocks.