Rise and decline of the fishery industry in the Aydarkul–Arnasay Lake System (Uzbekistan): effects of reservoir management, irrigation farming and climate change on an unstable ecosystem

Originally, a shallow saline depression between the Kyzylkum and the Nurata mountain range the Aydarkul–Arnasay Lake System (AALS) was created in 1969 when a catastrophic flood event in the Syr Darya catchment exceeded the capacity of the Chardarya reservoir. Additional water diversions further increased the volume of the lakes to up to 42.2 mln m³ in 2006. After the breakdown of the commercial fishing in the Uzbek part of the Aral Sea in 1983, the AALS became the most important fishery lake in Uzbekistan with an annual catch of more than 4600 tons (in 1988). In recent years, however, the fish catch experienced a sharp decline (down to 728 tons in 2006) due to the increased inflow of drainage water from the large Golodnaya Steppe (Hunger Steppe) irrigation scheme (e.g., 0.1 km³ in 1960, 1.0 km³ in 1970, 2.3 km³ in 1980, 2.9 km³ in 2000 and 3.6 km³ in 2010) and a decrease in freshwater inflow from the Chardarya reservoir (e.g., 4.0 km³ in 1995, 2.3 km³ in 2005 and 1.8 km³ in 2010). The increasing anthropogenic pressure, as well as the impacts of the climate change (+0.6–0.9 °C between 1950 and 2000, decrease in the long-term precipitation and increase in the variability), is threatening this ecological and economic important lake system. This article presents new data about the temporal dynamic of the lake hydrology (size, volume, water balance), the surrounding climate and its development as well as about the water quality of the lakes and the main drainage water collectors, and the development of the fish fauna over the last decades. This study, based on official data (Uzhydromet, Uzryba), online databases (GHCN) and extensive field work (water quality and fish sampling), provides a complete published analysis of the status quo of the AALS. Therefore, it is an important contribution to the establishment of a stable lake ecosystem system and a sustainable fishing industry.