Access to the Caspian Sea, the Persian Gulf, the Gulf of Oman, and many river basins provides Iran the potential to develop excellent fisheries. The government assumed control of commercial fishing in 1952. One government-owned enterprise, the Northern Sheelat Company, was established in 1952, and a second, the Southern Sheelat Company, was established in 1961. In recent years, illegal and off-season fishing, discharge of industrial and agricultural pollutants, overfishing by other Caspian littoral states, and other unfavorable conditions have endangered Caspian fish resources. Between 1990 and 2004, Iran's total annual Caspian Sea catch declined from 98,000 tons to 32,533 tons, including 463 tons of sturgeon, which yields high-quality caviar.