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Changes to the Fish Populations in the Upper Stream of Labe, which is Caused by Sudden Fluctuation of the Water Flow in the River.
HOCK, Lukáš
The aim of my work was to evaluate the influence, on the fish comunity, by the short term abnormal water flow in the upper stream of Labe, during the boating competitions. The monitoring of the fish comunity took palce in 7 localities, before the begining of the competition and after the competition during May, 2011. Each locality had been fished out in its total width and in a length of 100 meters. In 6 identical locations. Fish marking with the help of elatomeric marking of Cottus gobio species was carried out.On the basis of obtained values and information, evaluation of the changes to the fish comunity which was caused by the artificial flood was carried out, where we compared values of abundance, biodiversity, equitability, dominance and size variation. With the second fish-out in the same localities, we counted the number of marked fish of the Cottus gobio species caught in the previous marking. The assessment of values took place mainly on the existing fished out species of Salmo trutta morpha fario, Cottus gobio, Salvelinus fontinalis, Oncorhynchus mykiss in the river. In total we fished out 799 pieces of fish before the artificial flood, from which 156 pieces were Cottus gobio, and after the artificia flood only 136 Cottus gobio were fished out, from which 25 were marked fish being caught and marked in the first test.
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