Changes in the Aral Sea ichthyofauna and fishery during the period of ecological crisis

Aboriginal ichthyofauna of the Aral Sea consisted of 20 generative‐freshwater species from seven families. After acclimatization in 1927–1963, the number of species increased to 34. The regulation of Syr Dar’ya and Amu Dar’ya river water flows, and increasing water withdrawals, primarily for irrigation, resulted in a declining lake water level, increasing salinization and changing habitat conditions, especially for reproduction. As a result, the spawning areas were greatly reduced, and because of worsening conditions for natural reproduction, fish catches in 1961–1976 decreased more than 4‐fold. The first signs of the negative impacts of salinization on fishes appeared in the mid‐1960s. Natural reproduction ceased by the mid‐1970s, and indigenous commercial fish fauna were lost by the end of the 1970s. Flounder‐gloss was introduced from the Black Sea in 1979–1987 to preserve the fishery, and it was the only commercial fish left by 1991–2000. Because of the water level decline, the Aral Sea became divided in 1989 into the Large and Small Seas. By the end of the 1990s, flounder became extinct in the Large Aral because of high salinity, as did other fishes. Decreasing agriculture activity has resulted in stabilized run‐off of the Syr Dar’ya to the Small Aral since 1988, creating a freshened water zone where indigenous ichthyofauna returned from lacustrine systems and the river. The ecological state of the Small Aral is improving, with some aboriginal valuable commercial fishes having reached numbers making their commercial catch possible once again.