State of ecosystem of Lake Khedo (Western Karelia) in conditions of fish breeding

The article highlights the analyzes of the ecosystem of Lake Khedo (Republic of Karelia) under conditions of growing anthropogenic load caused by using the lake for breeding trout in fish cages based on the proper and literature data. Comparative analysis of hydrochemical data before the operation of the farm (until 2005) and after showed a twofold increase in water color (70-150°), which indicates an increased content of organic pollutants (humus, peat, silt). Also in the reservoir there are increased nitrogen and phosphorus compounds. Previously, the concentration of total phosphorus did not exceed 0.01 mg/l, today it reaches 0.02 mg/l. The main factor contributing to the satisfactory state of Lake Khedo is the high water flow rate, due to which most biogens are flown outside the lake. The data on the main hydrobiological indicators of the lake (phytozooplankton and zoobenthos) are presented. It has been stated that if earlier the reservoir corresponded to the mesohumous oligotrophic type, at present it reaches the initial level of mesotrophy, which is probably facilitated by the long-term cage cultivation of the aquaculture object. In terms of the abundance of organisms of the initial trophic levels, the reservoir corresponds to α-mesotrophic type. The lake is inhabited by 8 species of fish, and the valuable ones include whitefish Coregonus lavaretus (L.) and vendace Coregonus albula (L.). The results of the research made it possible to clarify the total production of commercial trout, which amounted to 300 tons per year and doesn’t exceed the total biogenic load. Recommendations on timing the regular ecological expertise of the lake and the adjustment of production volumes are given