Biology and conservation of sturgeon and paddlefish

The Acipenseriformes (sturgeon and paddlefish) live in the Northern Hemisph ere; half of these species live in Europe, mostly in the Ponto-Caspian regi on, one third in North America, and the rest in East Asia and Siberia. They reproduce in freshwater and most of them migrate to the sea, either living in brackish water (Caspian, Azov, Black and Baltic Seas) or in full seawat er on the oceanic continental shelf. Most species feed on benthic organisms . Puberty usually occurs late in life (5-30 years of age) and adult males a nd females do not spawn on an annual basis. Adults continue to grow and som e species such as the beluga (Huso huso) have reached 100 years of age and more than 1,000 kg weight. Stocks of sturgeons are dramatically decreasing, particularly in Eurasia; the world sturgeon catch was nearly 28,000 t in 1 982 and less than 2,000 t by 1999. This decline resulted from overfishing a nd environmental degradation such as: accumulation of pollutants in sedimen ts, damming of rivers, and restricting water flows, which become unfavorabl e to migration and reproduction. Several protective measures have been inst ituted; for example, fishing regulation, habitat restoration, juvenile stoc king, and the CITES listing of all sturgeon products including caviar. In a ddition, sturgeon farming presently yields more than 2,000 t per year (equi valent to wild sturgeon landings) and about 15 t of caviar. Hopefully, this artificial production will contribute to a reduction of fishing pressure a nd lead to the rehabilitation of wild stocks.