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Rozvoj zooplanktonu v rybnících s produkcí rychlených stádií hospodářsky významných druhů ryb
PECHA, Oldřich
This master thesis was focused on zooplankton development in ponds with advanced fry rearing of economically important fish species. For the purpose of my study, we sampled pond cascade that is managed by Štičí líheň - ESOX, spol. s r.o. in the village Liderovice, near Tábor. In this particular pond cascade, the annual production of advanced fry of economically important fish species takes place, namely pike, pikeperch, carp, tench and grass carp. Importantly, pond cascade is used several times during one growing season, and zooplankton is the main food source of all early stages of rared fish. For the production of advanced fry of fish served 3 ponds, which were released and refilled 2-3 times a season. Fourth pond served as a control stocked with one year old carp throughout the whole season. The water from an upper pond in the cascade served as zooplankton inoculum to a lower pond after the pond harvesting. Statistical analyses showed that the fry of different fish species in ponds lying in the same cascade does not affect the composition of zooplankton after restocking and water refilling. The only difference we noticed was in the treatment with pikeperch, which partially does not share the food base of other monitored species.We also found out, that the occurrence of Cyclops vicinus, Daphnia magna, D. ambigua or D. pulicaria was positively correlated with increased P-PO4 concentrations. We also confirmed that pond ecosystem can effectively retain nutrients from basins and use them for its production. As was shown after a short rain when the measured concentration of total phosphorus in the inflow in our pond system was 0.50 mg/L, on the contrary in the last pond of our cascade we measured values below 0.08 mg/L. High transparency was maintained in the whole cascade throughout the monitoring period, and an adequate economic profit was generated. Such management can be applied to only a few ponds (systems).
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Methodology of predatory fish quantification in reservoirs and lakes.
Blabolil, Petr ; Jůza, Tomáš ; Vašek, Mojmír ; Peterka, Jiří
The publication contains an evaluation of surveying 36 reservoirs and artificial lakes in the years 1985–2020 in different parts of the Czech Republic by four sampling methods, which are further divided according to the sampling environment, daily periods and targeted age groups of predatory fish. The methods are gillnets, seines, trawls and continuous boat electrofishing. The catchability, standardized and relative abundance of asp, pikeperch, pike and catfish are evaluated. Based on these data, the reader can decide which method to use to detect a particular predatory species and compare the results with the situation in other localities.
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Final report on ichthyologic work under the project C. J1620240 in 2016.
Kubečka, Jan ; Matěna, Josef ; Čech, Martin ; Blabolil, Petr
Young-of-the-year pike fry was stocked artificially along the left bank of the reservoir Švihov in May 2016. In July 2016 fingerlings inhabited mostly the shallowest littoral. Densities ranged from 1 to 2 pc 100m coast in the dam part into 7-8 pieces per 100 m of the coast in the middle part. Sampling pike fingerlings in the littoral zone has a high efficiency (estimate 84%). Any other observations (installing traps, scuba diving, sampling electrode farther from shore) show that pike fry did not occur at greater depths than most shallow littoral to about half a meter. The densities of fry at the right and left bank of the reservoir apparently did not differ. Even very small pike are probably able to swim across the large reservoir. Of the 81 individuals of pike fry with food 77.8% had a fish prey, and 17.3% had insect larvae in the gut.
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The formation of biogenic amines in flesh of selected fish species
MATĚJKOVÁ, Kateřina
The thesis deals with the use and effectiveness of some less common methods of conservation of fish meat. The formation of biogenic amines in meat is observed in connection with the non-traditional preservative methods. Amines can serve as indicators of protein degradation. The quality of fish was considered in connection with the increasing content of selected biogenic amines (putrescine, cadaverine, spermidine, spermine, 2-fenylathylamine, histamine, tyramine and tryptamine). Ultra performance liquid chromatography (UPLC) was used as the method for determination of biogenic amines. Amines were derivatized by dansylchloride before their UPLC separation. The fish flesh was vacuum-packed. Samples were stored for several weeks in a thermostat at the selected storage temperature after the application of selected preservative technique. Beta-irradiation and high hydrostatic pressure were used for the preservation of fish flesh. Control samples were not exposed to the â-irradiation and high pressure. The organoleptic properties were studied for all samples (smell/odor, insight and shape). Beta-irradiation was applied to fish meat of common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss). Both these species of freshwater fish are economically significant. Carp and trout are the species being mostly consumed in the Czech Republic. Fish meat is considered to be provided the flesh is fresh. A testing series of samples was created with common carp to determine the appropriate dose of â-irradiation. The maximum permissible dose of irradiation for fish meat is 3 kGy. Fish samples were exposed this dose in the first experiment. The dose of irradiation was reduced in following experiments based on the experience from the initial experiment. The doses of 0.25, 0.5, 0.75, 1.0 and 2.0 kGy were applied to rainbow trout. The value of 0.75 kGy of â-irradiation or higher (1.0, 2.0 and 3.0 kGy) prolonged the shelf life of fish meat, which was stored for three months (98 days). Prolonging of the shelf life of fish meat to approximately 98 days at 3.5 °C is redundant from technical point of view. For that reason lower doses 0.25, 0.5 and 0.75 kGy were tested in more detail in the repeated experiment with carp meat. Lower doses of â-irradiation are considered to be more acceptable and-at the same time-sufficiently effective for delaying the beginning of degradation processes. 6 High hydrostatic pressure was applied to meat of common carp (Cyprinus carpio), rainbow trout (Oncorhynchus mykiss) and pike (Exos lucius). Pike is another very popular kind of freshwater fish. Pike flesh is very tasty, but in spite of this, pike is not so much popular among consumers compared to carp and trout. The cause is its high price. Samples of pike were stored at standard temperature 3.5 °C and also at higher temperature 12 °C (unlike experiments with â-irradiation). Lower temperature of storage (3.5 °C) followed the conditions of storing of fish meat in industrial refrigeration facilities and households. The high pressure might not be sufficient for preservation at higher storage temperatures. This assumption was based on available information. Samples were treated by high pressure and stored at both 3.5 °C and 12 °C to verify this assumption. Higher temperature simulated either failure of refrigeration equipment or unsuitable store temperature of meat. In all species selected freshwater fish two levels of high pressure were applied ? 300 and 500 MPa. Both levels had significantly reduced the formation of biogenic amines, especially in samples stored at 3.5 °C. At this temperature, the effect of 300 and 500 MPa delayed start of degradation processes in fish meat by 3?4 weeks. At 12 °C and 500 MPa, high pressure extended the sustainability of meat by no more than one week. 500 MPa is effective treatment at the lower temperature of 3.5 °C. High pressure is not reliable preservative techniques at higher temperature.
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