|
| |
|
|
European catfish (Silurus glanis, Linneus 1758): Is the global warming the main reason of increasing of catches of the largest freshwater predator in Europe?
Bakeš, Michal ; Čech, Martin (advisor) ; Černý, Martin (referee)
European catfish (Silurus glanis, Linneus 1758) is our only fish which amount of catch is growing in our country in the last thirty years. The main goal of my work is to find out if global warming is essential for increasing catch of catfish, or whether rising temperatures are marginal, and the main reason is growing focus of fishermen on catfish. This thesis summarized knowledge about effect of global warming on ecosystems mainly on freshwater bodies that seem to be the most influenceable among terrestric ones. The enlarging populations of catfish in countries of south Europe (e.g. Spain, Italy) where catfish was recently introduced can be explained by the fact that warm water is suitable for catfish. However, some socioeconomic studies carried out in the Czech Republic as well as abroad clearly demonstrate that popularity of catching of catfish increases in time. I verified this idea by the results of my questionnaire survey, where 82 % of respondents approved that the popularity of catfish among fishermen is highest in the last decade. Based on the evidence we can say that increasing temperatures has a positive effect on the metapopulation of catfish in the Czech Republic, but this influence seems to be marginal. The main reason for still increasing catch is very likely the change of preferences...
|
|
|
Influence of feedstuff and breeding technology on changes of common carp´s (Cyprinus carpio L.) and of european catfish´s (Silurus glanis L.) mass quality
ZAJÍC, Tomáš
The work is focused on the nutrition and farming technology influences on the changes of the quality of common carp (Cyprinus carpio L.) and european catfish (Silurus glanis L.) meat. For the first experiment were used 6 groups of fish (common carp). Five of those were fed on cereals (maize, wheat, triticale, rye and barley), the sixth group was left on natural food by way of the control group. For the second experiment were used two groups of fish (european catfish). The first group was bred by the classical technology in fresh water ponds using natural food (dietary fish) by way of the control group. The second group was bred intensively in warm water in controlled conditions using feed compouned. In both of groups were defined following characteristics: weight yield, sensoric analysis, content of nitrogen compounds, fat content and spectrum of fatty acids in fat. It was ascertained that the rearing technology affects the results in all monitored characteristics. The biggest attention was payed to the results of fatty acids spectrum. While in the test using common carp was proved a higher proportion of PUFA (inclusive EPA and DHA) in the control group, in the test using catfish was this proportion higher in intensively reared group.
|
|
|
Changes of biochemical parameters in fish after nitrite exposure
PODLESNÝ, Martin
The aim of this thesis was to assess the effects of long-term nitrite exposure on mortality, growth rate and blood biochemistry in rainbow trout (Oncorhynchus mykiss). Furthermore, acute toxicity tests with nitrite were performed on rainbow trout (Oncorhynchus mykiss) and sheatfish (Silurus glanis). The theoretical part focuses on aquatic toxicology including toxicity evaluation of substances and preparations for water organisms. Detailed information on nitrite are summarized there, namely information on nitrite occurrence and sources in aquatic environment and the mechanism of their uptake and toxic influence on fish including factors influencing their toxicity. The practical part consists of methodology and results of acute toxicity tests on rainbow trout and sheatfish and sub-chronic test on rainbow trout. According to the acute toxicity tests results, 96hLC50 values were estimated at 11.2 mg.l-1 NO2- for rainbow trout and 15.3 mg.l-1 NO2- for sheatfish. Sub-chronic exposure of rainbow trout to nitrite concentrations ranging from 0.01 to 3.0 mg.l-1 lasting 28 days caused an increase of glucose concentration and a decrease of potassium concentration in the blood plasma among all experimental fish compared to control. Elevated nitrite levels were found in the plasma of the fish exposed to concentrations of 0.6 mg.l-1 NO2- and greater. The plasma nitrite levels did not reach those applied in any experimental group in the present study. At highest nitrite concentration (3.0 mg.l-1 NO2-), 42 % growth inhibition and 65 % mortality among fish was noticed. On the basis of growth rate inhibition data, the values of NOEC and LOEC were estimated at 0.01 mg.l-1 and 0.2 mg.l-1 NO2-, respectively.
|
|
|
The fishery management results with the wels catfish (Silurus glanis) in the selected reservoirs (fishing-grounds of the Moravian Anglers Union)
Prokeš, Miroslav ; Baruš, Vlastimil ; Peňáz, Milan
Long-term development (1951-2003) of wels catfish catches in the fishing-ground Dyje 7 (Moravian Anglers Union) was characterized. Moreover, results of wels fisheries in six dam reservoirs (Plumlov, Vranov, Brno, Letovice, Mohelno, Mušov) were also analysed. In the fishing-ground Dyje 7 the annual wels catches, during so-called riverine period (1953-1975), were 7.9 individuals (0.13 inds.hectare-1) and 31.9 kg (0.53 kg.hectare-1). The mean individual weight was 5.18 kg. During the lake period (1982-2003), the catches became significantly higher: 88 ind. (0.17 inds.hectare-1) and 1342.6 kg (2.58 kg.hectare-1). The mean individual weight was 11.62 kg. With respect to amount of catches, the start of so-called wels phase appeared roughly in the17th year of the Mušov Reservoir operation.
|
guest ::
