National Repository of Grey Literature 67 records found  beginprevious37 - 46nextend  jump to record: Search took 0.01 seconds. 
Diurnal vertical migrations of zooplankton in a stratified mountain reservoir
Adámek, Radek ; Hořická, Zuzana (advisor) ; Stuchlík, Evžen (referee)
The thesis - a literature review - was aimed at the phenomenon of diurnal vertical migration (DVM) of zooplankton, in relation to particular conditions in the Josefův Důl reservoir in the Jizera Mountains (northern Bohemia, Czech Republic). The area of the Jizera Mts has a very sensitive geology, and thus suffered a strong anthropogenic acidification in the second half of the 20th century. The consequence was a long-term degradation of chemistry and biology of soils and surface waters. The waters in the upper plateau of the mountains were fishless, with a low diversity and biomass of both the phytoplankton and zooplankton. Recovery from acidification is slowest in the deepest reservoir, Josefův Důl. Due to its morphology, thermal stratification, newly re-stocked brook charr population, and invertebrate predators' occurrence, the zooplankton distribution in the vertical profile is expected to be irregular, with DVM. The following diploma project, oriented to seasonal changes and vertical distribution of the zooplankton in the Josefův Důl reservoir, should contribute to long-term data on biological recovery of the reservoirs from acidification, and explain the role of biotic parameters in zooplankton succession.
Reciprocal predation between non-native crayfish and salmonids Who eats whom?
MÜLLEROVÁ, Lucie
Signal crayfish (Pacifastacus leniusculus) is important invasive species in European freshwaters. Its influence on other freshwater organisms is well known from the literature, as well as direct and indirect impact on fish assemblages. This work was focused on the experimental evaluation of non-indigenous signal crayfish as a predator of salmonids compared to indigenous noble crayfish (Astacus astacus). Moreover, the possible importance of young-of-the-year signal crayfish as a prey for salmonids was assessed. There were carried out experiments using eggs and hatchings of grayling (Thymallus thymallus) as a prey for adult and subadult specimens of both, signal and noble crayfish. Next experiment used young-of-the-year signal crayfish as a prey for young-of-the-year of brown trout (Salmo trutta). Results showed that the danger of signal crayfish for grayling eggs is slightly higher. However, detected differences were surprisingly lower and in the majority of parameters even insignificant. In the case of grayling hatchings, was not detected any significant difference at all. The abilities of both tested species to prey on eggs and hatchings are therefore very similar, comparable. Even so, the effect of signal crayfish can be importantly higher in natural conditions because of its more dense populations, higher growth rate and fast maturation. In accordance to our findings, it is evident that brown trout has no so high effect of crayfish juveniles compared with crayfish effect on salmonids early developmental stages. Crayfish are therefore more likely able to limit salmonids than conversely.
Bioacoustics in frogs
Karochová, Lucie ; Šandera, Martin (advisor) ; Schneiderová, Irena (referee)
This thesis is focused on bioacoustics in frogs. The purpose was to compare known informations about vocalization types, influence of sexual selection on males call, chorusing behavior and influence of predation. Bioacoustics research was carried on many frog species from different part of world, with most experiments being carried on neotropical frogs, specifically Physalaemus pustolosus. Acoustics communication is a wide-spread phenomenon across the animal kingdom. The theme of bioacoustics is studied quite extensively. The most studies is focused on birds or mammals, and the study of frogs, especially the European species, is poorly known. The influence of sexual selection on males vocalization is well known, while research in other evolutionary principles such as the effect of predator is studied only marginally. Research on new types of frogs tend to focus on the description of vocalization types that occur in a given species. In addition to in detail are studied individual voice parameters such as frequency or intensity and chorusing frogs are determined mainly by call-timing or synchronization. Newly was discovered ability of some frogs generate ultrasonic harmonies and surprising discovery was female vocalization as well. Generalization of facts is quite difficult because of the lack of...
Morphological strategies of photoautotrophic protists under various environmental conditions.
Ševčíková, Tereza ; Kulichová, Jana (advisor) ; Pichrtová, Martina (referee)
The aim of this thesis is to provide a comprehensive overview of morphological adaptation of photoautotrophic protists to various environmental conditions and to describe the influence of their shape and size for different life strategies. Thesis summarizes overview of the main factors affecting the natural mikroalgal community and shows their relevance for life of photoautotrophic protists. These factors include availability of nutrients, pH, temperature, penetration of light and predation. Next part focuses on different methodological approaches and attitudes, how to investigate, measure and explain morphological features.
Distribution and ecology of the turbellarian Dugesia tigrina in the Vltava river and selected Prague brooks and its interactions with native turbellarian species
Sevruková, Natálie ; Mourek, Jan (advisor) ; Hanel, Lubomír (referee)
Key words: (Dugesia tigrina), ecology, bioindication, predation, Vltava, Prague The main goal of my thesis was the research of occurrence and ecology of planarians of the group Ttricladida in the Vltava River and some brooks flowing through the territory of Prague. The emphasis was given on the non-native North American species - Dugesia tigrina. The research can be divided into field surveys of population size and ecological requirements of planarians and a laboratory experiment, in which I have investigated the predation behavior of planarians. During my fieldwork, which took place from August 22th to November 11th 2009, I have found out that the Dugesia tigrina occurs only in the Vltava river, in six of the nine studied localities. During the research it was not found in the studied brooks. It chooses localities with a natural shoreline, deeper ground, rapid water and it lives in company of mainly Dugesia polychroa. It appeared at moderately polluted places. During the predation experiment, which ran from December 17th 2009 to October 20th 2010 at a temperature of 14 řC and triple repetitions in all mutual combinations of five planarian species, intraspecific cannibalism and frequent asexual reproduction of Dugesia tigrina was comfirmed. The experiment showed mainly preying of indigenous...
The role of nest in reproduction of the Great Reed Warbler
Jelínek, Václav ; Procházka, Petr (advisor) ; Krist, Miloš (referee) ; Trnka, Alfréd (referee)
7 Abstract Bird nests protect eggs and nestlings, allowing the parents to leave their offspring and subsequently return to them. Their thermoregulatory properties reduce energetic costs of incubation and brooding of nestlings. For all these reasons, nests are key structures for the reproduction of a majority of avian species and as such they should be subject to natural selection. Several hypotheses describing selection pressures which affect the size of nests or some of their parts have been suggested. In my PhD thesis, I investigated some of them in the great reed warbler (Acrocephalus arundinaceus) - an open nesting passerine species with very variable nest size. For this purpose, I used a large dataset of several hundred measured great reed warbler nests, nest enlargement experiments and an experiment with artificial nests. In accordance with previous studies, we did not find that nest size affects the probability of common cuckoo (Cuculus canorus) brood parasitism, while it was influenced by other factors, such as timing of breeding, reed density around the nest and nest visibility from the nearest potential cuckoo perch site. More interestingly, we found that cuckoos adjust their nest-searching strategy in relation to availability of host nests. When host nests were scarce, cuckoos parasitized all of...
Factors influencing seed germination, emergence and mortality in soil seed bank of Bromus sterilis L.
Žďárková, Veronika ; Soukup, Josef (advisor)
Bromus sterilis L. (barren brome) spreads rapidly in many European regions. In the Czech Republic, its importance has increased dramatically over the past 10 years. Barren brome is reported as a problem weed in winter crops such as winter wheat, winter barley and oil seed rape, in vineyards and in other cultivated places. Barren brome has been becoming troublesome weed of winter cereals mainly in reduced soil tillage systems. The factors, that are important for its spreading and adaptability under different environmental conditions, are dormancy and germination. Optimal timing for seed germination varies with respect to natural conditions and it is determining for plant development. These traits are adapted to different conditions and habitats; therefore the dormancy and germination response patterns to those conditions vary significantly. Recently there are not many information available on germination behaviour, therefore this study was focused on seeds of barren brome and its characteristics, which were collected in different regions of the Czech Republic. Seeds were investigated under different temperatures, light regimes and water stress in a wide range of conditions. The following characteristics of seeds were studied the dormancy, the dynamics of germination, the temperature optimum, the age of seeds and dynamics of emergence from different depths and persistence in the soil profile under field conditions. Dormancy and germination are influenced by external conditions. The dormancy of seeds barren brome is very short or missing. The germination is influenced by light; the seeds germinated better under darkness than under light regime. The primary dormancy of B. sterilis was short and the seeds needed only three weeks for after-ripening. The seeds of B. sterilis showed broad ecological valence to hydrothermal factors germinating in the wide range of 3 to 35 °C. The temperature optimum is 5-23°C. The germination was only slightly influenced in an environment with low water potential. Germination was limited under water stress only at lower temperatures under 10°C. The response to light at various temperatures showed that seeds germinated better in darkness in all temperatures regimes, than in alternating light regime, especially at lower temperatures. The emergence declined significantly with burial depth (under 40 mm). The seeds were not able to survive in the soil seed bank for a longer time and fall seeds lost viability after 1 year burial in soil profile. These results may be of value for development of predictive models and understanding period when weed control may be most feasible.
The evaluation predation of pheasant nests in Prague and vicinity
Melecká, Radka ; Kušta, Tomáš (advisor) ; Tomáš, Tomáš (referee)
The graduation Theses deals with a predation of pheasants nests. The aim of this work was to observe predation of the nests in model areas in the neighbourhood of Prague. There were chosen two natural parks such as Draháň Trója and the natural reserve Údolí Únětického potoka which is located between Praha Suchdol and Únětice village. The intention of our work was to map an occurrence of pheasants predators and consequently evaluate the biggest risks of pheasants nesting. Within the evaluation of predation of the nests we have also set artificial pheasants nests located on the sunny places of bushes and arable land of mentioned locations. Interesting results were collected; concretely in the valley of Únětický potok was predated up to 35% of artificial nests and in Draháň as much as 85%. Between the main predators belonged the fox (Vulpes vulpes), martens (Martes spp.), pied mannikin (Pica spp.) and wild boar (Sus scrofa). Based on these results was made a conclusion that there is a suitable game management provide by the local hunting organization. We have made a recommendation to build up more interim and lasting covers feeding hoppers and bio corridors for pheasants. In the area of Draháň was recommended to apply for a special statutory exception to reduce predators on not huntable lands by catching trapping.
The Impacts of Non-native Species American Mink (Neovison vison) on Native Fauna
Moucha, Pavel ; Vrabec, Vladimír (advisor) ; Jan, Jan (referee)
The American mink is among the weaselly (Mustelidae) carnivore native to North America. It is a food opportunist living semiaquatic lifestyle. He is very well adapted to the new environment. And he was introduced by humans as a furry animal to many areas of Europe, Asia, South America and other areas. Secondarily often he escaped or were released into the wild, where he managed very well prosper and continue to reproduce. To the Czech Republic came as a furry animal in 20. to 30. years of the last century, in the wild he was then observed since the 60s. This study examines the impact of American mink on our fauna, especially in view of the food spectrum. The research was conducted in the middle of the river Berounka in Křivoklát from December 2014 to December 2015. The aim of the study was to capture the largest possible number of minks during the summer and in winter. Another aim was whether mink dangerous for the local population of reptiles. Trapping took place during the 552 trapping night. a total of 20 were trapped mink. This means that the average captured 1 mink to 28 trapping night. Of these 20 individuals were 5 females and 15 males. It caught up to 8 mink in the winter and 12 in the summer. Based on the analyzes were 7 mink (35 %) excluded from the analysis because of an empty stomach. The largest component of food mink accounted for 76.16 % mammals for example order: Rodentia eg. vole (Microtus arvalis), muskrat (Ondatra zibethicus). Other food components formed on the same level with a share of 7.69 % reptile grass snake (Natrix Natrix), birds (order: Passeriformes) and fish (class: Actinopterygii). The last component of food occurring in the samples was 0.77 % of the insects (orders: Coleoptera, Lepidoptera). In the analysis wasn´t detected representative of the class of amphibians (Amphibia). The food spectrum in the winter and summer season was no different. At-risk populations reptile shows finding snakes in the stomach mink. An important outcome of this study is also alert to legislative issues concerning the mink in the Czech Republic and the possible effects on the otter (Lutra Lutra).
Monitoring of invasive spiny-cheek crayfish in Lipno dam and the evaluation of its predation on chosen fish species.
SALON, František
Astacologic survey took place in ÚN Lipno and was conducted in time from 2012 till 2013. For the actual mapping of the occurrence of spiny-cheek crayfish, the locations of total 17 places were detected. These monitoring areas were carried out in two ways for collecting the samples. The trapping of all individuals was achieved with special instruments, like pots or traps by hands or with the help of nets. For the caught specimens of spiny-cheek crayfish, which were determined by sex, the length of carapace was measured and as well if possible, the postorbital carapace length was taken. Throughout the whole monitoring, 228 individuals of spiny-cheek crayfish were caught in the amount of 107 (47%) females (CL = 21.5 ? 7.3 mm) and 121 (53%) males (CL = 20.1 ? 5 mm). Another aim of this work was to demonstrate that crayfish figure in fish food menu. Catches of fish were carried out in two ways, using fishing rods or into the clutches. The stomachs and intestines contents were analyzed at caught fish samples. If the condition of the contents of stomachs or intestines were allowed, it was also identified, what kind of food it was. For our annual issues, were included mainly species of piscivor fish. Spiny-cheek crayfish were identified in the stomachs of two species of fish, namely perch and pike.

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