| Aquaculture is currently the world's fastest growing animal-producing sector. The Khorezm province in southwestern Uzbekistan has over 450 small lakes that could be developed for aquaculture, diversifying the local economy and providing rural communities with an additional source of protein. It is hypothesized that the Khorezm lakes have adequate water quality and the necessary physical and biological properties to support healthy fish populations that are safe for human consumption. For this thesis, four lakes in Khorezm were chosen for analysis to answer the research question: are Eshan Rabat, Khodjababa, Shur (Koshkopir) and Tuyrek lakes suitable for developing aquaculture? To assess lake suitability, water quality data as well as biological and physical characteristics of the lakes were analyzed for these four lakes in Khorezm. From June 2006 to October 2008, the four lakes were sampled monthly to determine temperature, pH, salinity, dissolved oxygen, nutrients, trace metals, pesticides and toxicity to organic contaminants. Fish, zooplankton, macroinvertebrates and algae samples were also collected. Lake surface sediments were tested for pesticides and trace metals, and lake cores were collected in 2008 and 2010 to provide information about lake age and to determine historical pesticide concentrations. Results indicated that Khodjababa, Shur (Koshkopir) and Tuyrek lakes are well-suited for raising fish species and that Eshan Rabat has the least favorable conditions to sustain fish populations. Temperature, pH, salinity, dissolved oxygen, and trace metals meet aquaculture guidelines in Khodjababa, Shur (Koshkopir) and Tuyrek lakes. Eshan Rabat showed higher salinity levels than the other three lakes, often above maximum tolerable levels for local fish species. This lake also had observed water temperatures that are lethal to fish. Nutrients in the four lakes were generally low, although high ammonium ion concentrations were occasionally observed. Pesticide and metal contamination in all four lakes was relatively low. Pesticide concentrations, specifically DDT and HCH, were above recommended water quality guidelines for aquaculture, but these pesticides did not appear to be accumulating or harming fish species in the lakes, although our fish sample size was very small. Sediment samples contained low levels of DDT, HCH and metals, which were all below consensus-based probable effect concentrations. With over 450 lakes in Khorezm, developing water resources to provide a local food supply could help increase consumption of fish, a traditional Uzbek food, while also providing an additional source of income for Uzbek farmers. |
