Six sturgeon species are found in the Caspian Sea and its drainage basin: Russian sturgeon (Acipenser gueldenstaedtii), Persian sturgeon (A. persicus), Stellate sturgeon (A. stellatus), Ship sturgeon (A. nudiventris), Sterlet (Acipenser ruthenus) and Beluga (Huso huso). The bulk of the world’s remaining stock of wild sturgeon resources is found in the Caspian, which also accounted in the past for between 80 and 90 per cent of total world caviar production. Since 1970, pollution from various sources, mainly from industry and agriculture in surrounding areas plus oil extraction activities, has had a major impact on the Caspian Basin and its ecosystems. Accumulations of various toxins in the main rivers surrounding the Caspian and in the sea itself have led to changes in the physiology and reproductive systems of sturgeon. In the period from 1985 to 1990, sturgeon dieoffs were recorded in the Volga and Ural rivers (Ivanov 2000). Up to 90% of sturgeon specimens examined showed muscle deterioration and shrinkage of the outer layers of eggs (Pavelieva et al., 1990). It is clear that the decline in recorded sturgeon catches is due to a decline in available stocks. Over a 30-year period, total sturgeon catches have declined dramatically - from 27 thousands tonnes to less than one thousand tonnes. The Great Sturgeon or Beluga (Huso huso Linnaeus, 1758) is the biggest and most valuable sturgeon, not only in the Caspian but in the world. In the early 1990s, the total annual catch of Beluga was about one thousand tonnes: in the 2000s the catch dropped dramatically with a total in 2007 of only 33 tonnes.
From collection: Caspian Sea - State of Environment 2011