Ninety percent of caviar comes from Caspian sturgeon. As recently as the mid-1980s, more than 30,000 tons of sturgeon were taken by Soviet and Iranian fishermen. By 1995, the official catch was down to 3,100 tons. The size of the individual fish has declined along with the tonnage of the catches. Today, the average weight of a caught sturgeon is around 80 pounds.
Caspian sturgeon is brought on board.
The decline has resulted primarily from rampant poaching, a rapid increase in pollution-related disease and loss of spawning grounds because of construction of dams on the rivers that feed into the Caspian. Like the salmon, the sturgeon swims from deep water into rivers to spawn. When access to the upstream spawning grounds is blocked, the fish can not reproduce. The World Bank has devised the Caspian Environment Project which includes programs, such as building fish channels and artificial spawning grounds, to help the sturgeon survive. The World Bank says contamination of the Caspian by DDT used in agriculture could be another factor contributing to the disappearance of the sturgeon because it could be a cause of infertility in the fish.