Biology and conservation of sturgeon and paddlefish

摘要

The Acipenseriformes (sturgeon and paddlefish) live in the Northern Hemisphere; half of these species live in Europe, mostly in the Ponto-Caspian region, one third in North America, and the rest in East Asia and Siberia. They reproduce in freshwaterand most of them migrate to the sea, either living in brackish water (Caspian, Azov, Black and Baltic Seas) or in full seawater on the oceanic continental shelf. Most species feed on benthic organisms. Puberty usually occurs late in life (5-30 years ofage) and adult males and females do not spawn on an annual basis. Adults continue to grow and some 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 1982 and less than 2,000 t by 1999. This decline resulted from overfishing and environmental degradation such as: accumulation of pollutants in sediments, damming of rivers. and restricting water flows, which become unfavorable to migration and reproduction. Several protective measures have been instituted; for example, fishing regulation, habitat restoration, juvenile stocking, and the CITES listing of all sturgeon products including caviar. In addition, sturgeon farming presently yields more than 2,000 t per year (equivalent to wild sturgeon landings) and about 15 t of caviar. Hopefully, this artificial production will contribute to a reduction of fishing pressure and lead to the rehabilitation of wild stocks.