National Repository of Grey Literature 42 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Diel activity of common bleak Alburnus alburnus in response to prey availability
Josefovičová, Anna ; Horká, Petra (advisor) ; Slavík, Ondřej (referee)
Fish behaviour and the structure of fish communities in rivers are known to be affected by various environmental factors. Turbidity imposes a considerable environmental constraint by influencing visibility and reducing the distance at which a predator detects prey. Previous studies have shown that fish become more active and extend their diurnal movements and home range size during the high turbidity period. However, this effect may also be associated with a lower food availability in turbid water and various other environmental factors like are day time, water temperature, discharge or oxygen concentration may also have an effect. This thesis present radio-telemetry study which examined factors influencing diurnal activity and home range size in common bleak Alburnus alburnus in riverine environment. The aim was to assess the response of bleak behaviour to various abiotic factors and prey availability, to establish the extent diurnal movements and home range size of bleak and to evaluate feeding strategy of fish. Four individuals of bleak were radio-tracked in the River Elbe during July - September 2007.The position of an individual fish was determined every three hours during one diurnal cycle, in total 10 diurnal cycles were recorded. During the same intervals, turbidity, water temperature,...
Theory-guided design of novel Fe-Al-based superalloys
Friák, Martin ; Holec, D. ; Jirásková, Yvonna ; Palm, M. ; Stein, F. ; Janičkovič, D. ; Pizúrová, Naděžda ; Dymáček, Petr ; Dobeš, Ferdinand ; Šesták, Pavel ; Fikar, Jan ; Šremr, Jiří ; Nechvátal, Luděk ; Oweisová, S. ; Homola, V. ; Titov, Andrii ; Slávik, Ondrej ; Miháliková, Ivana ; Pavlů, Jana ; Buršíková, V. ; Neugebauer, J. ; Boutur, D. ; Lapusta, Y. ; Šob, Mojmír
Our modern industrialized society increasingly requires new structural materials\nfor high-temperature applications in automotive and energy-producing industrial\nsectors. Iron-aluminides are known to possess excellent oxidation and sulfidation\nresistance as well as sufficient strength at elevated temperatures. New Fe-Al-based\nmaterials will have to meet multiple casting, processing and operational criteria\nincluding high-temperature creep strength, oxidation resistance and room-temperature\nductility. Such desirable combination of materials properties can be achieved in multi-phase\nmulti-component superalloys with a specific type of microstructure (the matrix contains\ncoherent particles of a secondary phase - a superalloy microstructure). In order to design\nnew Fe-Al-based superalloys, we employ a state-ofthe-art theory-guided materials design\nconcept to identify suitable combinations of solutes.
Age structure and growth of wild brown trout in relation to population density and habitat quality
Závorka, Libor ; Slavík, Ondřej (advisor) ; Matěna, Josef (referee) ; Reichard, Martin (referee)
Brown trout Salmo trutta L. is a fish species with high socio-economic value, which is favourable among anglers and a successful invader worldwide. The aim of this thesis is to explore environmental factors affecting body growth and survival of brown trout with emphasis on density dependent selection in juvenile life stages. This thesis is specifically focused on: (1) effect of population density on growth and survival with respect to a dynamic of a local group of individuals (papers I and II); (2) effect of inter-individual differences in behaviour on the relationship between individuals life-history traits and available resources (papers III and IV); (3) link between demo-genetic structure of population and growth and mortality rates of individuals (papers V, VI and VII). Datasets for this thesis were collected during a long-term mark-recapture study on wild brown trout population (2005-2011) in the catchment of the Otava River in Šumava National Park (Czech Republic) and a set of field and laboratory studies conducted on wild populations in streams on west coast of Sweden. In accordance with some previous studies, this thesis showed that growth of juvenile brown trout is negatively affected by population density. Nonetheless, this thesis reveals that the negative effect of density dependent...
Spatial distribution of the European catfish Silurus glanis influenced by familiarity
Fořt, Martin ; Slavík, Ondřej (advisor) ; Kozák, Pavel (referee)
One of the key elements of animal social behaviour is the recognition of individuals on the basis of previous experience. This relationship is called familiarity and affects individual's behaviour. We know many examples of familiarity-based behaviour among fish. Many results show that familiarity is advantageous. Familiar individuals are less aggressive, forage more, make more cohesive shoals and grow faster. We tested the influence of the familiarity on the spatial distribution of juvenile wels catfish Silurus glanis from two unfamiliar groups, which were held in separate tanks. In a laboratory experiment was the spatial distribution of individuals monitored in the artificial stream by using passive integrated transponders. Shelters, which were occupied by individuals, were placed in the stream. Two groups of fish were subsequently added into the experiment under conditions of limited or unlimited shelters. These groups came from the same tank (so they were familiar) or from different tanks (so they were unfamiliar). 1080 individuals were used in this experiment and over three million individual fish positions were recorded. We discovered changing levels of activity under different conditions. When we compared activity of original and additional individuals, we measured higher level of activity in...
Proximate control of sexual dimorphism in livebearer Poecilia wingei
Farkačová, Klára ; Kratochvíl, Lukáš (advisor) ; Slavík, Ondřej (referee)
The effect of 17α-methyltestosterone a 17β-estradiol on sex of livebearer fish Poecilia reticulata and P. wingei was studied. Solution of 2.5 mg testosterone was added in the aquarium the first and fifteenth day after delivery of new fry. Estrogen was administered in food to gravid females (400 mg per 1 kg food). Sex of all individuals was determined in one, two and three months. Administration of neither testosterone nor estrogen caused sex reversal; in the second case reproduction of almost all females was stopped.
Mutual interaction of multiple cracks growing in the particulate composite with brittle matrix under conditions of sub-critical crack growth
Slávik, Ondrej ; Ševeček, Oldřich (referee) ; Majer, Zdeněk (advisor)
In the first part of the submitted diploma thesis, the knowledge in the sphere of the fracture mechanics, related to the practice part of this thesis are summarized. In that the 2D parametrical numerical model of the particle composite with multiple cracks was created, using the finite elements method. Thanks to this model it is possible to find specific configurations which are showing the existance of multiple mutual interactions between these cracks, just by simple manipulation of the input data. In the calculations the influence of the residual stresses was considered which are formed during production of the material. The effect of the subcritical crack growth was taken into account as well in this thesis.
Seasonal variation of activity and pathogen prevalence in populations of the spiny-cheek crayfish
Matasová, Klára ; Petrusek, Adam (advisor) ; Slavík, Ondřej (referee)
The most widespread of invasive crayfish in the Czech Republic is the spiny-cheek crayfish (Orconectes limosus). It is a major disease carrier of crayfish plague, caused by the pathogen Aphanomyces astaci. The infection is lethal to European native species of crayfish. Transmission of this disease is usually associated with the spread of crayfish, which is dependent on their movement. The main aim of this work was to evaluate the differences in crayfish migratory activity in the Pšovka brook among seasons, and assess the factors that may affect it, by the use of radiotelemetry and trapping. We tested the hypothesis that crayfish use brook in the period from spring to autumn and then return back into a pond to overwinter. Furthermore, we evaluated how far from the pond crayfish migrate, and whether there is any relationship between migration and the season or water temperature. The results demonstrate that the activity varies among seasons (being strongly affected by breeding season) but in most studied periods did not significantly depend on water temperature. According to our monitoring, the spiny-cheek crayfish does not spread substantially to upstream parts of the Pšovka. Seasonal migration between the pond and the brook was monitored using two-way flow-through traps installed at the mouth of...
Density dependent growth of brown trout Salmo trutta in oligotrophic streams
Závorka, Libor ; Slavík, Ondřej (advisor) ; Frouzová, Jaroslava (referee)
This thesis deals with the influence of population density on the growth of brown trout Salmo trutta. The research was carried out in the Šumava National Park in the river basins of two oligotrophic streams, the Vydra and the Křemelná. Data has been collected between years 2005 and 2010, every spring and autumn. Fish were caught via electrofishing and the length and weight of each individual were measured. Every individual caught was marked in a unique way. A few samples of scales were taken from some of them. The scales were fixed into laboratory slides, scanned and measured by graphic software. According to the differences between annual lamellas density, the age and the annual growth of individual's body length were estimated. Thanks to these results a negative relationship between the individuals' of age 1+ growth rate and the population density was confirmed. The importance of this thesis is mainly in comparing the influence of different spatial and time definitions of population on this relationship. The influence of the population density in spring (the initial time of the growth period) was proved to be essential for the growth rate. This fact suggests the importance of compensation growth intensity after the long period of winter for individual's general growth under conditions provided by...
A behaviour of the European catfish Silurus glanis in the mating season and for rest of the year with focus on social interactions among individuals
Lüftner, Radek ; Slavík, Ondřej (advisor) ; Randák, Tomáš (referee)
Reproduction ability is the key factor for survival and dispersal of every species. There is, however, only limited information about reproduction of large-bodied fish. Males of European catfish, our biggest native fish, build nests in vegetation and mate there later with females. After succesful mating male guards the nest and takes care of eggs and fry. According to literature, the act of reproduction should take place at nights with water temperature from 18 to 24 řC. However, available records about reproductive behaviour are outdated, fragmentary or come from aquacultures. Thus, a study was designed to evaluate behaviour of European catfish in their natural environment in the Berounka river using radiotelemetry, the results of which I processed in this thesis. Spatial distribution of catfish was followed during the whole year, with special attention on separating mating season from the rest of the year. The goal was to determine conditions characteristic for the mating period and to verify that catfish in the field indeed reproduce in pairs. For this purpose, 10 adults were tracked for two-year period (2002-2004) in the Berounka river by radiotelemetry. Exact positions of all individuals were followed in fourteen-day cycles. In every tracking episode, the position of an individual fish was...

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28 Slávik, Ondrej
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