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Habitat preferences of the members of the family Chydoridae (Crustacea, Cladocera)
Zimová, Tereza ; Sacherová, Veronika (advisor) ; Šorf, Michal (referee)
This thesis is a literature review of ecological niche of some species of Cladoceran family Chydoridae. The aim of this work is to summarize the knowledge about the occurrence of species in various types of environments and what are their preferences or see which factors are limiting for them. This work is focused on the type of habitats in which they are found, the trophic state of water and pH. It also mentions to a lesser extent environmental factors such as concentration of calcium and water depth, which might also influence the niche choice of these species. Species can be divided into opportunists with a wide niche and specialists with a narrow one, yet a large proportion of species have a wide tolerance to most environmental factors. Key words: Chydorids, niche, habitat, macrophytes, open water, pH, trophic state, depth, calcium
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Fish detection with modern sonar systems
TUŠER, Michal
This dissertation thesis was focused on improving the methodology to detect fish with modern sonar systems in lakes and reservoirs. The first part of the thesis is aimed to the vertical beaming acoustics with a key focus on the acoustic dead zone and its practical solution. The second part deals with the fish orientation in reservoir?s open waters and its consequences in horizontal beaming acoustics. The last one dedicates to the DIDSON multi-beam sonar and its reliability in detection and sizing of fish.
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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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