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This article gives an overview the impact hydroelectric power facilities on ichthyofauna and river ecosystems. Issues addressed include the destruction of fish by grates and turbines; disturbances in the hydrological regime of rivers; changes in the water physicochemical regime resulting from damming; the muddying of spawning and feeding grounds. Suggestions are made for counteracting these disadvantageous transformations. This is achieved by equipping hydroelectric facilities with appropriate safety devices that lead fish away from the facility to a secure place where they can swim safely downstream, and also eliminate sharp fluctuations in water level that can occur below dams. It was determined that none of the existing methods eliminate ichthyofauna losses. It is recommended to combine several protection methods such as grates and electric barriers. Due to the negative impact hydroelectric plants have on the ichthyofauna, it is essential that the energy consumers participate in the costs of fish stocking to compensate for losses.
Pollution and degradation of rivers clearly affect fish. A decrease in the number of fish species and in population size is less visible. While studying this problem, the author takes as examples the vimba and trout, fish feeding in the sea, with spawning grounds in the sub-Carpathian Vistula tributaries (Dunajec, Raba, Wisłoka, San). The dam built in 1968 in Włocławek on the Vistula river brought about a fall in the number of fish above the dam. The author suggests coordination of hydrotechnical and environmental activities.
The ichthyofauna of the Warsaw section of the Vistula River as well as selected water bodies in Warsaw was described. The information was collected from catches, analysis of stocking registers as well as interviews with anglers carried out between 1989 and 2002. The existence of 40 fish species was noted, including 33 species in the Vistula River. 3 to 11 species, belonging to eurytopic and stagnophilic ecological guilds, was registered in particular water bodies. The results indicate that diversified fish assemblages exist in Warsaw water bodies that are subject to high anthropogenic pressure, including rich fish assemblages in the Vistula River.
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