STATE OF ZOOPLANKTON OF IK LAKE (OMSK REGION) IN RELATION WITH CHANGING ECOLOGICAL CONDITIONS
Ik Lake is one of the largest ponds of Omsk region. The latest surveys of the lake were conducted from 2010 till 2016. This work provides hydrological and hydrochemical characteristics of Ik Lake. It shows species compositions of zooplankton, size of its population, biomass, and production. During the survey period 28 species of the following planktonic animals were detected: 7 species of the Rotifera, 14 species of Copepoda, and 7 species of Cladocera. Analysis of long-term dynamics of zooplankton development in Ik Lake showed that number of planktonic animals in summer was pre-determined by the Cladocera and Copepoda complex, while the Cladocera formed the basis of size of the population and biomass. Variety of species, size of the population, and biomass of zooplankton differed considerably depending on water level and mineralization, temperature and gas conditions of the lake, species composition, and density of fish population. During the survey period average size of the planktonic animal population in summer fluctuated from 9.45 to 35.83 thousand specimens/ m<sup>3</sup>, while their biomass fluctuated from 0.57 to 3.75 g/m<sup>3</sup> with the average level of 1.48 g/m<sup>3</sup>. On the basis of calculation of production of forage organisms potential fishing productivity of the lake was determined. Zooplankton reserves of Ik Lake makes it possible to expect fishing productivity of 10-66 kg/ha or 71-469 tons of fish products from the lake on the whole. We noted prospects of use of this lake for breeding valuable fish feeding on zooplankton.