EFFECT OF WATER CHESTNUT (TRAPA NATANS) ON CONDITIONS OF FISH JUVENILE FATTENING IN THE KIEV RESERVOIR

Purpose. Investigation of the effect of higher aquatic vegetation growing on shallow water areas of the Kiev reservoir on conditions of spawning of commercial fish species and growth of their juveniles. Methodology. Materials for the study were higher aquatic plants, the number of which was counted with the aid of a 1 x 1 m frame. Bottom deposits for determination of the biomass of benthic organisms were collected using dredges of different constructions. Fish juveniles were caught using beach seine. Dissolved oxygen content was measured with the aid of the thermooximeter AZhA-101M. Findings. It was found that during last years, shallow water areas of the Kiev reservoirs are characterized by rapid colonization with higher aquatic vegetation. The most abundant among them is water chestnut, the number of which reaches 75 %. Its number on some areas of the upper part of the reservoir reaches 75 plants per 1 m2. During summer, with water temperature of 25 ? 27 0С, a reduction of dissolved oxygen content to 0,5 ? 0,7 mg/L was observed that resulted to fish kills. A dependence of the number of benthic organisms from vegetation type, which grows on these areas, was found. It was found that fish juveniles are absent on areas, where water chestnut predominated. Originality. Every year, areas covered by water chestnut considerably expand that result in deterioration of hydrological regime of the reservoir. Significant siltation of bays due to slowdown of water current is observed. Reduction of oxygen content in water leads to decrease of both benthic organisms and fish juveniles. Practical Value. It is recommended to conduct a complex enhancement of shallow water areas of the Kiev reservoir but due to the fact that water chestnut is listed in the Red Book of Ukraine as a protected species, it is prohibited to conduct such enhancement works aimed at reducing areas covered by this species.