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How shall we study the fish stock of our large water reservoirs?
Kubečka, Jan ; Matěna, Josef ; Čech, Martin ; Draštík, Vladislav ; Frouzová, Jaroslava ; Hohausová, Eva ; Jarolím, Oldřich ; Jůza, Tomáš ; Kratochvíl, Michal ; Muška, Milan ; Peterka, Jiří ; Prchalová, Marie ; Říha, Milan ; Tušer, Michal ; Vašek, Mojmír
Quantitative fish stock assessment recently advanced significantly in the Czech Republic. Sampling of open water was facilitated by application of scientific echosounders, trawls, Nordic multimesh gillnets, purse seines and booming electoshockers. Simplified combination of the above methods was recommended for the monitoring of larger stagnant water the Water Framework Directive of EU. Combination of all above approaches with more classic ones (beach seining, benthic gillnets) is being used for „complex fish stock assessment“ providing the assessment of abundance, biomass, species and age composition of all important species in all important habitats of the reservoirs. Further improvements of results is likely to be achieved by the application of multibeam acoustic cameras and by mitigation of the problems connected with quantitative trawling of large fish
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Drinking water reservoir Nýrsko - influence of macrophytes on water quality
Hejzlar, Josef ; Hohausová, Eva ; Komárková, Jaroslava ; Kopáček, Jiří ; Peterka, Jiří ; Duras, J.
The importance of macrophytes in P cycling was studied in Nýrsko Reservoir, an oligotrophic water body in western Bohemia. A comparison of the external P loading with the P content in macrophytes of Nýrsko Reservoir in 2004 demonstrated that macrophytes can play a significant role in P-cycling also in deep, pelagial-dominated water bodies on condition that the external P loading is low and macrophytes have appropriate conditions for their growth (mainly small extent of water level fluctuation). Nýrsko Reservoir is an apparent example of situations from limnological textbooks when macrophytes function as a stabilizer of the aquatic ecosystem with an efficient zooplankton grazing on phytoplankton allowing suitable water quality for drinking water production.
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