Changes in the Aral Sea ichthyofauna and fishery during the period of ecological crisis Z. K. Ermakhanov, 1 I. S. Plotnikov, 2 * N. V. Aladin 2 and P. Micklin 3 1 Aral branch of Kazakh Research Institute of Fishery, Aralsk, Kazakhstan, 2 Laboratory of Brackish Water Hydrobiology, Zoological Institute of RAS, Universiteskaya naberezhnaya, St. Petersburg, Russia, 3 Deptartment of Geography, Western Michigan University, Kalamazoo, MI 49008, USA Abstract Aboriginal ichthyofauna of the Aral Sea consisted of 20 generative-freshwater species from seven families. After acclimati- zation 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 salini- zation 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 improv- ing, with some aboriginal valuable commercial fishes having reached numbers making their commercial catch possible once again. Key words Aral Sea, ecological crisis, fishery, fishes. INTRODUCTION Located in the arid zone of Central Asia, until the 2nd half of the 20th Century, the Aral Sea was a single termi- nal water body – a huge closed lake into which two rivers – Syr Dar’ya in the northeast and Amu Dar’ya in the south flowed. The island Kokaral divided the Aral Sea in two parts, including the smaller northern (Small Aral) and larger southern (Large Aral). The depression filled with the Aral Sea consists of several smaller ones. Because of such a structure, the Aral Sea became divided into separate waterbodies as the water levels dropped over the decades. The average salinity of most of the Aral Sea was 10 g L )1 , so-called brackish conditions. The Aral Sea, over several centuries prior to the 1960s, preserved its quasi-stable state. For the period of more recent observa- tions (from the middle of the 19th Century), its water level fluctuated a few metres, primarily because of natural climatic factors (Micklin 2010). The aboriginal ichthyofauna of the Aral Sea, except for species found only in completely freshwater areas, consisted of 20 species from seven families (Table 1; Nikolsky 1940). The richest in species was the family Cyprinidae (12 species), accounting for 60% of all fish fauna. Based on species diversity, the second was the family Percidae (three species). Each of the other fami- lies – Acipenseridae, Salmonidae, Siluridae, Esocidae and Gasterosteidae – were represented by only one species. There were no endemic fish genera and species in the Aral Sea, with endemism only on the sub-species level. It is possible to explain this situation as a function of the youth of the Aral Sea as an isolated waterbody (Nikolsky 1940). *Corresponding author. Email: aral3@zin.ru Accepted for publication 11 September 2011. Ó 2012 The Authors Doi: 10.1111/j.1440-1770.2012.00492.x Journal compilation Ó 2012 Blackwell Publishing Asia Pty Ltd Lakes & Reservoirs: Research and Management 2012 17: 3–9