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Influence of fish pond management, land use in catchment and climate change on species composition of blue-green algae blooms
Kroupová, Kristýna ; Stuchlík, Evžen (advisor) ; Pivokonský, Martin (referee)
The aim of the thesis was to explain expansion of cyanobacterial blooms and the change of their species composition in surface standing waters during the last 2-3 decades as a result of fishery management, land use in catchments, and climate change. Cyanobacteria possess a range of unique and highly-adaptable eco-physiological traits, which enable them a mass occurrence and a dominance over the other phytoplankton groups under recent anthropogenic changes (nutrient loading and rising temperatures). Moreover, many species of cyanobacteria produce cyanotoxins, which increase their resistence against zooplankton grazing and cause severe deterioration of the water quality. In consequence of changes in fishery management (a decrease in the use of superphosphate as a fertilizer during the year 1970), the fish stock density increased and the clear water phase disappeared. This is responsible for a change in species composition of cyanobacterial water blooms. Summer blooms of Aphanizomenon flos-aquae were replaced with A. flos-aquae var. klebahnii. The current composition of water blooms in ponds differs considerably from the typical composition in the 1990s. For example, recent expansion of Woronichiniana naegeliana is caused by the higher stock densities and the shift from a two-year cycle of fishery management...
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The fishery management results with the wels catfish (Silurus glanis) in the selected reservoirs (fishing-grounds of the Moravian Anglers Union)
Prokeš, Miroslav ; Baruš, Vlastimil ; Peňáz, Milan
Long-term development (1951-2003) of wels catfish catches in the fishing-ground Dyje 7 (Moravian Anglers Union) was characterized. Moreover, results of wels fisheries in six dam reservoirs (Plumlov, Vranov, Brno, Letovice, Mohelno, Mušov) were also analysed. In the fishing-ground Dyje 7 the annual wels catches, during so-called riverine period (1953-1975), were 7.9 individuals (0.13 inds.hectare-1) and 31.9 kg (0.53 kg.hectare-1). The mean individual weight was 5.18 kg. During the lake period (1982-2003), the catches became significantly higher: 88 ind. (0.17 inds.hectare-1) and 1342.6 kg (2.58 kg.hectare-1). The mean individual weight was 11.62 kg. With respect to amount of catches, the start of so-called wels phase appeared roughly in the17th year of the Mušov Reservoir operation.
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