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Crayfishes as a prey
MAN, Milan
Due to the increase in the number of non-native species of crayfishes and their presence on more and more localities, there is the possibility of their elimination using predatory fish species. The length relationships between a prey and a predator could clarify this possibility. The aim of this bachelor thesis was to develop high quality literary review about the incorporation of crayfish into the food chain and processing samples of a perch (Perca fluviatilis) from a locality with an occurrence of juvenile crayfishes (Astacus astacus). I wanted to verify the possibility of a perch predation on juvenile crayfish individuals. However, only three crayfishes were found in the analyzed perchs. After a very low percentage of crayfishes in the analyzed perchs, a laboratory experiment was carried out with young of the year of signal crayfish (Pacifastacus leniusculus) and perchs. Unfortunately, this experiment ended unexpectedly. The crayfishes were served to perchs, but the fishes showed no interest in them throughout the experiment. The results of food analysis show, that smaller perchs are able to eat crayfish, but they are not a sought-after component of their diet. In this case, the low frequency of crayfishes in the diet was caused by enough other food (insect larvae) and also the number of shelters in the pond, where the crayfishes were reared. In the experiment, I unfortunately failed to confirm the positive relationship between a perch as a predator and a juvenile crayfish as a prey. However, the conclusions of the other studies on the use of larger perchs show the preference and high frequency of occurence of juvenile crayfishes in their diet.
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Study of fish-passing facility on the weirs on Bečva river
Chovancová, Kateřina ; Veselý, David (referee) ; Milerski, Rudolf (advisor)
This master's thesis consists of three main parts. The first section describes some types of fish crossings and basic information of their design. There is also marginally described program HEC-RAS. The second part is about the Zuberská weir and Osek stage. I review here fish ladders according to the original drawings in the HEC-RAS and suggest possible options to address these passable fish crossings for the fish crew. The last section is devoted to Mikulenkov weir where the fish crossing has been completely removed. Here I propose a new fish ramp according to modern knowledge and applicable standards. I also review the proposed fish ramp in the HEC-RAS program in order to verify the hydraulic characteristics.
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Fish detection with modern sonar systems
TUŠER, Michal
This dissertation thesis was focused on improving the methodology to detect fish with modern sonar systems in lakes and reservoirs. The first part of the thesis is aimed to the vertical beaming acoustics with a key focus on the acoustic dead zone and its practical solution. The second part deals with the fish orientation in reservoir?s open waters and its consequences in horizontal beaming acoustics. The last one dedicates to the DIDSON multi-beam sonar and its reliability in detection and sizing of fish.
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Occurrence of perfluorinated compounds in fish from rivers of the Czech Republic
HOLAŇ, Viktor
The object of this thesis is the assessment of fish contamination by selected foreign substances as perfluorinated compounds. these sites were selected for the thesis' purpose: Bečva - Dluhonice, Elbe - Přelouč, Bílina - Usti nad Labem, Jizera - Předměřice, Sázava - Nespeky and Otava - Topělec. Fish were caught by electrofishig. The concetrations of contaminants were measured in fish muscle and liver. The analysis were performed using liquid chromatography (HPLC - MS / MS). Concentrations of PFOS, PFNA, PFOA, PFHxS and PFHpS in fish muscle and liver tissues were monitored.
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HYGIENIC QUALITY OF FISH FROM SIGNIFICANT FISHING WATERS BEROUNKA 1, LUŽNICE 6, OTAVA 4, OTAVA 7 (P)
BARTOŇ, Jiří
The main aim of this study was to evaluate hygienic quality of fish from significant fishing waters: Berounka 1, Lužnice 6, Otava 4, Otava 7 (P). Sampling was performed in 2010 by electrofishing and fishing rods. 173 individuals belonging to 13 different fish species were fished. The samples of fish muscle were analysed for the following substances: Hg, Pb, Cd, PCB, DDT and its metabolites (DDE and DDD), a-HCH, b-HCH, y-HCH, HCB. Samples of bream (Abramis brama) muscle were collected at all monitored sites (exception was Otava 7) and bream was used as reference species to compare the contamination among monitored rivers. The results were compared with valid hygienic limits. The values of contamination were in most cases very low and far below the limits. Only mercury was identified as a risk contaminant in all monitored rivers. Average concentrations of mercury in the muscle of bream were in the range of 0.261-0.284 mg/kg and were comparable in all rivers. The hygienic limit for mercury (0,5 mg/kg) was exceeded only in 4 cases - one individual sample of bream from Otava, two mixed samples of asp (Aspius aspius) from Berounka and Lužnice, one mixed sample of perch (Perca fluviatilis) drom Otava. The highest value of total mercury content (0.768 mg/kg) was found in asp from Lužnice 6. All concentrations of persistent organochlorinated pollutants in fish muscle were far below the valid hygienic limits. The only health risk was posed by increased content of mercury.
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Exercise aquaculture production in the Czech Republic
PŘÍBORSKÝ, Josef
This work evaluate dynamic properties of production of Czech market fish in the last decade of twenties century and the beginning of twentyonce century first together. Then separately by several fish species, by using of them (home trade and export, sale in vivo or processed) and evaluate causes of these changes. It uses resources mainly from the Czech Fish Union in České Budějovice, from customs statistics and Czech Ministry of Agriculture. Carp is the most breeded fish, in the market dominate the native fish. In term of consumption is trout the second most significant fish. Without carp are stocked also less amount of supplementary fish. Freshwater fish, by results, stabilize their own position on the Czech market. Also important is export into other European countries, where successfully compete especially by quality of carp meet.
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The Mercury Content in Fish from the Jordán Resesvoir in Tábor.
KUBECOVÁ, Jana
The aim of those study was to find out an up-to date content of mercury in the tissues of fish in the dam reservoir Jordan in Tabor. To compare particular fish according to their species, age and dietary strategy and their capability to accumulate mercury. The distribution and the mutual rates of total content of mercury in particular tissues of carnivorous and non-carnivorous species of fish were determined (muscle, liver, kidneys). Dedicated atomic absorption spectrophotometer AMA 254 was used to determine the total content of mercury. The results show that exceeding the former hygienic limit 0.1 mg.kg-1 w. w. in the muscle of non-carnivorous fish with almost all samples. It was the low-age carnivorous species of fish was probably the cause that the hygienic limit (0,5 mg.kg-1 w. w.) was exceeded only rarely (in the muscle a five-year-old asp, Aspius aspius, 0,888 {$\pm$} 0,041 mg.kg-1 w. w.). The pond Kosin located above the dam reservoir Jordan was exploitation as a comparative locality. The average content of mercury in the muscle of selected indicator species of fish in the reservoir Jordan - bream large (Abramis brama) at the age of 5 years - it was 0,241 {$\pm$} 0,080 mg.kg-1 w. w., whereas from comparative locality, from the pond Kosin, for the same species and age of fish it was only 0,045 {$\pm$} 0,008 mg.kg-1 w.w., i.e. more than five times more of the content in comparison with an unweighted locality. The realized results also show that the burden of the fish with mercury for a common consumer does not exceed neither the {\clqq}hazard index`` (HI) nor the toxicological limit ( the maximum recommended ration a week from the food is 1,6 {$\mu$}g MeHg per 1 kg of body weight according) to the WHO. However, with more intensive consumption of mainly carnivorous fish from the reservoir Jordan, e.g. of the sport fishermen´s family members, it could cause risk from this consumption ( i.e. HI > 1). Further work should be aimed at monitoring of the content of mercury in the tissues of mainly predators of higher age category.
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The Methods of the Sensorial Appraisal of the Fish Meal Quality
TOMEČEK, Ondřej
The methods of the sensorial quality assesment, mainly by the new products in the market, are still a very important part of the business strategy. After killing fish there are changes in the whole organism and these can appear in the product characterization in various ways. These changes of the sensorial marks (smell, taste, aftertaste and consistence) are judged according to the form of the quality criteria. There are various methods for the judgement of the sensorial profile of the picked fish product and this is practised either by means of the machines or by the subjective judgement of the educated experts. Fish meal, mainly that of fresh water fish, is a type of commodity which should be enforced and which seems to have a good perspective in the market. That´s why learning these methods and of course their subsequent application is very important for the demand of fish meal and fish products by the exacting consumers.
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