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Vliv biomanipulací s účelovou rybí obsádkou na vývoj kvality vody vodárenské nádrže Hamry
Jurek, Lukáš
I have dealt in my thesis with biomanipulation on the water reservoir Hamry. The reservoir is located near the village Hamry in the Bohemian-Moravian Highlands, it is meso-eutrofního character and its size (about 42 ha of water surface) and an average depth of 2 m is ranked among the smaller, shallow tank. Biomanipulation measures are there implementation and monitored in the long term (since 2008).Biomanipulation implemented in 2015, which mainly consist of removing unwanted species of fish from the reservoir were implemented by different methods at all ontogenetic levels of fish. That means collecting eggs perch Perca fluviatilis, L., seinings of juvenile stages panktivorous species of fish, as well as seinings and elimination of adult unwanted fish species. Part of the seinings were catching spawning shoals of bream Abramis brama, L. and roach Rutilus rutilus, L. With those biomanipalition actions was carried collection and evaluation of samples of zooplankton, phytoplankton, hydrochemical analyzes and physico-chemical parameters of water. Also were investigated phosphorus content in sediments. Some of the data I obtained and evaluated actively (especially zooplankton), other data were evaluated by specialists from ÚBO AV ČR Brno, or employees of the Department of Fisheries and Hydrobiology at the Institute of Zoology, Fisheries, Hydrobiology and Apiculture MENDELU Brno and I have only used this data to compare the efficiency of the imlpemented biomanipulation.
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Biology and invasive spreading of signal crayfish (Pacifastacus leniusculus) in the Vysočina Region
JUREK, Lukáš
This thesis deals with the issue of non-native crayfish species in Europe, focusing mainly on the Czech Republic. The main species of interest was the signal crayfish. Its biology in relation to invasive spreading was evaluated. The most recent list of its known populations in the Czech Republic was compiled. These data were subsequently compared, updated and enriched with new locations based on this field monitoring. Its occurrence was evaluated largely in the Vysočina Region, in the area of Velké Meziříčí. As it turned out, the center of the signal crayfish occurrence in the Czech Republic is located really in the area of its original introduction thirty years ago in our country, in the vicinity of the Velké Meziříčí. During that time, signal crayfish have successfully expanded into the surroundings waters, both naturaly (downstream and upstream migration) and with human aid (with restocking fish, direct distribution by the public). It occupied all possible types of habitats, from running waters of the two major rivers Balinka and Oslava to their tributaries creeks of different size and character. It found suitable living conditions also in some ponds, particularly those less intensively farmed. Signal crayfish was recorded in areas, where noble crayfish Astacus astacus is still relativelly widely present, in some place even forming sympatric populations. The work was also focused on epibionts Branchiobdella sp., their presence or absence on caught crayfish. Their occurance was also recorded and evaluated.
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