|
|
Rybí společenstva pěti vodárenských nádrží v povodí Moravy
Jurajda, Pavel ; Janáč, Michal ; Roche, Kevin ; Mikl, Libor ; Šlapanský, Luděk ; Krechler, I. ; Adámek, Zdeněk ; Jurajdová, Zdenka ; Halačka, Karel
Cílem této pilotní studie bylo přinést základní data o rybích společenstvech pěti, doposud jen málo prozkoumaných, vodárenských nádrží.
|
|
|
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.
|
|
| |
|
| |
|
|
Gobiidae - food competitors for our native fish species?
Všetičková, Lucie ; Jurajda, Pavel ; Vašek, Mojmír ; Adámek, Zdeněk ; Roche, Kevin
To date, two species of the non-native Gobiidae family have been recorded in the Czech Republic: the tubenose goby (Proterorhinus semilunaris) and round goby (Neogobius melanostomus). The aim of this study was to assess the dietary habits of these two species, with the relationship between goby diet and that of native species (potential competition, predation) of particular interest. Early results suggest that the main dietary items of both gobiids are common benthic invertebrates such as Chironomidae, Trichoptera and Ephemeroptera. Fish eggs and fry were rarely taken by either species and, when taken, consisted almost exclusively of eggs and fry of their own species (cannibalism). In addition, the round goby was shown to be necrophagous, scavenging on large fish carcasses. This behaviour si relatively rare in the Czech fish assemblage. Our results suggest that tubenose and round goby, while not predating heavily on native benthivorous species, may still represent possible competitors.
|
|
|
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.
|
|
| |
|
| |
guest ::
