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Ichthyological survey and evaluation of biomanipulation measures at Hamry reservoir in 2015
Jurajda, Pavel ; Adámek, Zdeněk ; Janáč, Michal ; Jurajdová, Zdenka ; Mikl, Libor ; Šlapanský, Luděk ; Roche, Kevin Francis ; Kopeček, Lukáš
This study, which has been running since 2008, examines the use of the Hamry Water Reservoir as a model for fish community biomanipulation studies with the aim of improving water quality. Of primary interest to the Reservoir administrators, the Elbe River Basin authority s.p., is the maintenance of high water quality for drinking purposes, thereby preventing conflict of interest with multiple stakeholders. In addition, the study aims to determine whether biomanipulation of fish communities can be undertaken effectively in a reservoir.
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Biomanipulation measures at the Hamry water supply reservoir - poor reaction of phytoplankton to planctivorous fish reduction
Jurajda, Pavel ; Adámek, Zdeněk ; Janáč, Michal ; Roche, Kevin ; Mikl, Libor ; Rederer, L. ; Zapletal, T. ; Koza, V. ; Špaček, J.
One measure commonly used for improving water quality in open waters is biomanipulation of fish stock. Previous studies in shallow lakes confirm the importance of reducing cyprinid populations for increasing zooplankton. Empirical results from reservoirs, however, are scarce. The aim of this study was to evaluate the effect of an intensive reduction of cyprinid fishes and perch fry density between 2009 and 2013 on water quality in the Hamry drinking water reservoir. The abundance of common bream broodstock decreased by around 12 000 individuals over the five years, and biomass dropped below 20 kg.ha-1. Stocking with pike and zander proved less effective. In reservoirs similar to Hamry, reduction of bream biomass can be a highly effective means of increasing filtering zooplankton biomass. Phytoplankton dynamics, however, appear to depend on additional factors, with nutrient loading (especially phosphorus) probably playing the primary role.
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