National Repository of Grey Literature 28 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Study of the limnological components of the ecosytem of Lake Medard in 2022.
Peterka, Jiří ; Hejzlar, Josef ; Nedoma, Jiří ; Znachor, Petr ; Seďa, Jaromír ; Vejřík, Lukáš
The report summarizes the research results of the limnological components of the ecosystem of the newly created Medard postmining lake achieved for the year 2022 and recommendations for further monitoring.
Evaluation of the intensity of poaching pressure on a water reservoir: the model case of ÚN Žlutice.
Vejřík, Lukáš
The report describes the intensity of poaching pressure on the Žlutice Reservoir.
Ellimination of unwanted fish species from dam reservoirs - Possibilities, efficiency and economic evaluation.
Jůza, Tomáš ; Blabolil, Petr ; Čech, Martin ; Draštík, Vladislav ; Holubová, Michaela ; Hůda, J. ; Kočvara, Luboš ; Kolařík, Tomáš ; Muška, Milan ; Peterka, Jiří ; Prchalová, Marie ; Říha, Milan ; Sajdlová, Zuzana ; Tušer, Michal ; Vašek, Mojmír ; Vejřík, Lukáš ; Kubečka, Jan
spontaneous development of populations and the influence of human interventions. For situations where a certain part of the fish population needs to be caught, within the project 'Biomanipulation as a tool for improving the water quality of reservoirs', we tested the available approaches in terms of their effectiveness and difficulty. The target species of catches were mainly cyprinid fish (bream, bleak, roach, rudd, white bream), which feed mainly\non zooplankton and tend to form very large populations. Among the most effective methods of catch during spawning are catches using electrofishing boats and fyke nets. In the non-spawning period, it is possible to carry out mass catches using trawl nets. Catches are effective both before spawning (in April) and during the summer. However, with repeated catches in the same places, their effectiveness decreases as a result of the fish being spooked. The efficiency of the catches partially improves again if the catches are repeated with a break of approximately 1–2 weeks. Catches also vary according to the stocking density of a given water body. With effective catches, the cost of catching 1 kg of fish is in the range of CZK 15–50.
Survey of European catfish population in Žlutice Reservoir in 2019
Vejřík, Lukáš ; Sajdlová, Zuzana ; Bartoň, Daniel ; Kolařik, Tomáš ; Čech, Martin
The report summarizes the results of monitoring the abundance, size structure, behavior and feeding of catfish food in the Žlutice Resevoir. It also contains conclusions and recommendations for the management.
Analysis of photo-records of non-fish prey in the diet of selected species of fish-eating birds
Mach, Jakub ; Čech, Martin (advisor) ; Vejřík, Lukáš (referee)
Piscivorous birds are often blamed for causing significant damage to fish stocks. Various methods are used to determine the composition of their food, each of them has limits in its ability to determine the complete food spectrum. This work maps the complete food composition of 14 species of fish-eating birds with a method that is not commonly used. Method used in this work uses analysis of publicly available photos on In addition to the complete composition of the food, the species composition of the non-fish part of the prey was also determined, and in the case of the Great Cormorant (Phalacrocorax carbo), also the length of the fishes it catches. The aim of this work is to reveal the usability of this method for these purposes. A total of 2350 retrieved photographs were analyzed. The results obtained by photo analysis are in all cases compared with data in the available literature. For representatives of heron birds (Ardeidae), the analysis of photographs provided good information on the food spectrum of individual birds and on the qualitative composition of the non-fish component. It also provided relatively good information on the diet of the White-tailed Eagle (Haliaeetus albicilla), but the bird part of the prey was slightly underestimated. In the diet of the Great Crested Grebe...
Study of the state of wels catfish population and its diet in the Římov reservoir in 2018
Vejřík, Lukáš
Based on the capture of wels catfish using longlines, the aim of the study was: 1. To estimate the abundance of catfish population, over 70 cm TL (total length), in 2017 and 2018. 2. O compare the abundance of catfish, expressed as catch per unit effort, with the other localities surveyed. 3. To determine the average length and weight of catfish. 4. To determine the proportion of artificially introduced and naturally stocked catfish into the reservoir. 5. To determine the annual growth of catfish on the basis of the catches of stocked pit tagged catfish and the size of the catfish identified in catches in 2017. 6. To evaluate the diet of catfish according to the stomach content analyses for 2017 and 2018.
Survey of the catfish population in the Klíčava reservoir in 2018
Vejřík, Lukáš
Based on the capture of wels catfish using longlines, the aim of the study was: 1. To estimate the abundance of the catfish population, individuals over 70 cm TL (total length). 2. To compare the abundance and size of catfish, expressed as the catch per unit of effort, with the other reservoirs surveyed under the management of the Vltava River Authority state enterprise (Žlutice and Římov). 3. To determine the average length and weight of catfish. 4. To evaluate the diet of catfish according to the stomach content analyses.
Survey of the European catfish population in the Žlutice Reservoir in 2017
Vejřík, Lukáš ; Peterka, Jiří
The aim of the study was to estimate the population density of wels catfish in the Žlutice Reservoir and to compare it with other localities studied, to determine the average length and weight of the catfish, to determine the proportion of artificially stocked and naturally reproduced catfish, to estimate the annual growth and to evaluate the catfish diet based on stomach contents. A summary of the work carried out and the results achieved are the content of this report.
Report on the survey of behavior and biomanipulation function of Europaen catfish population in Římov Reservoir in 2017
Říha, Milan ; Vejřík, Lukáš ; Peterka, Jiří ; Kubečka, Jan
Report summarizes our research of behavior and movement of wels catfish (Silurus glanis) in the Římov reservoir in years 2017-2018. Data about behavior and distribution were collected using a positioning telemetry system.
Biology of predatory fishes in dam reservoirs and lakes
This Ph.D. Thesis is focused mainly on the biology of two typical European predatory fishes, European catfish (Silurus glanis) and perch (Perca fluviatilis). Catfish is a typical apex predator, whereas perch is a smaller species that plays role of a mesopredator. Although, catfish is the third largest freshwater fish in the world, only few studies dealing with this species have been revealed thus far. The main reason is connected with capturing of the species that is inefficient by standard ichthyologic methods. Studies, that have been revealed recently, focused mainly on expansions of catfish to the West and South Europe. Catfish is unwanted in these localities due to a potential negative impact on native fish community, thus its reduction is desirable. In contrast, catfish occurrence is important in native localities where it plays a key role as a biomanipulative species (I). Catfish is a true generalist, which is a typical feature for large-bodied apex predators connected with high energy consumption of their bodies. The second typical feature is a wide diet plasticity and thus good adaptability to new food sources. It is associated with distribution of various food sources among individuals within the population (II). By contrast, perch is one of the most studied fish in the world and hundreds of studies with IF are revealed every year. However, the more information about biology of perch have been known, the more questions have been arisen. Several phenomena are revealed also in this thesis. For instance, crucial impact of juvenile perch on the entire ecosystem is described. High predation pressure on zooplankton may induce piscivory in primarily zooplanktivorous fish (III). Further, juvenile perch utilize hypoxic pelagic zones as a refuge against predation (IV). The last surprising phenomenon is described in the study dealing with both species, catfish and perch. Their coexistence may lead in strong discrimination of one species caused by special predation that was supposed to be implausible (V).

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11 VEJŘÍK, Lukáš
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