This dissertation provides an overview of the status of critically endangered sterlet in the Czech Republic and in other countries located in the Danube river basin. Results of own research of artificial breeding at experimental and farm conditions are presented. In the results section, focus was placed on most problematic part of artificial reproduction, development, growth and offspring rearing of sterlet in technological aquaculture. The specific objective pursued by the sterlet were: method of non-invasive detection of gas in the digestive tract by radiologic imaging, the effect of different environmental conditions for the presence of gas in the digestive tract and assessment of broodstock for spawning, followed by offspring rearing.

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The thesis summarizes findings from the field of initial rearing of sterlet (Acipenser ruthenus) that are currently available. The results of experimental rearing, which took place in 2014 and consisted of two parts, are included. In the first part, the impact of the exchange rate of the water in the tanks on change of hydrochemical parameters. For the experiment three variants in duplicate were prepared, with different flow rate for each one. The volume of water in the tanks was set to 100 liters and the number of fish was 150 fish/tank. Water change rate within the first variant was set for 1/3 of volume per hour, within the second variant for 1/3 of volume per hour and within the third variant for 3/3 of volume per hour. Each day was measured oxygen content, water temperature and pH, and samples for laboratory analysis were being taken. The results were analyzed by analysis of variance. No statistically significant difference has been found between monitored parameters, therefore these flow rates had no impact on the change of hydrochemical parameters for each variant. In the second part of the experiment was compared the effect of three different feed mixtures on growth parameters and development of fish. The same conditions of the rearing environment were maintained, but stocking density was reduced to 50 fish/gutter and a uniform water change rate of 3/3 volume per hour was set. The first variant was presented feed Aller Bronze 2 mm, the second variant Aller Silver 2 mm and the third variant Biomar Inicio 918 2 mm. At the beginning of the experiment, the fish reached an average piece weight of 29.00 g and FWC 0.44 within the first variant, 29.70 g and FWC 0.43 within the second variant and 29.31 g and FWC 0.41 within the third variant. At the end of the experiment the fish reached monitored parameters with following values: the first variant had the average piece weight of 37.99 g, FWC 0.41, SWGR 0.90 %.d-1, FCR 2.12 kg.kg-1 and PER 1,01; within the second variant, the average piece weight was 40.38 g, FWC 0.41, SWGR 1.02 %.d-1, FCR 1.82 kg.kg-1 and PER 1.18; within the third variant, the average piece weight was 43.51 g, FWC 0.40, SWGR 1.44 %.d-1, FCR 1.44 kg.kg-1 and PER 1.46.

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Using of recirculation systems for rearing of fish is common practice in Western Europe countries. Benefits of this systems are utilized in recovering programs of endangered species of fish. In this work we had paid attention on suitability of RAS for rearing Nase, Vimba bream and Barbel. In the first part two six-month experiments were conducted. The five-month-old nase and vimba bream had been trained on pellet feed and acclimated to four different temperatures. The WT fluctuated in parallel with ambient outside conditions at an average of approximately 4 °C for the inflow system and approximately 15, 18 and 21°C in closed, recirculation systems. The total length and weight were measured at two-week intervals and SGRw, FCR and survival were monitored. We observed a positive effect of higher water temperatures on their growth rate of each species. Both groups (WT 21°C) had the most rapid growth and highest SGRw. Growth rate and SGRw were lowest for each species in group with the ambient temperature conditions. Lower temperature at the level of 18°C gave good results in comparison to rearing in cold water. Individual weight was 3.25 and 4.13 times higher for nase and vimba bream, respectively. The temperature 15°C was chosen with regard to the functioning of the biofilter and in this experiment, it proved to be a minimal temperature suitable for rearing of river fish species in RAS. The economic costs to maintain this temperature is low, but the effect of production considered this level of WT as very less effective in several aspects. To conclude this part, we found intensive winter rearing of nase and vimba bream is an effective way to prepare fish for spring restocking. In the second part we have tested suitability of Vimba bream as a trainer fish for adaptation of pikeperch for commercial pellet diet. One of the basic problems in pikeperch culture in RAS is adapting early life stages to pelleted feed (PF). Our work compares four different ways of adapting 6-week-old pikeperch fingerlings to feeding on a commercial diet. The methods were designated, A - use of trainer fish and direct application of PF; B - use of trainer fish and gradual addition of PF with natural food (NF, chironomid larvae); C - direct application of PF only; D - gradual addition of PF with NF. The growth trial experiment (including adaptation to PF) lasted 14 days by which time all experimental groups were accepting PF. Pikeperch fingerlings in group A grew significantly faster and PF was more readily accepted compared to other groups. Other characteristics observed (total weight increment, FCR) also support the use of trainer fish and direct application of PF for pikeperch in their adaptation to intensive culture. The aim of the final study were to compare the effect of anaesthetics MS 222, clove oil, 2- phenoxyethanol and Propiscin on haematological and blood biochemical profiles in vimba bream. The haematological and blood biochemical profiles of vimba bream anaesthetized with MS 222 (100 mg/l), clove oil (33 mg/l), 2- phenoxyethanol (0.4 ml/l), Propiscin (1.0 ml/l) and non-anaesthetized control group were tested. Each tested group was divided into two subgroups. The first subgroup was sampled immediately after 10-min anaesthesia. Second subgroup was sampled 24 h after 10-min anaesthesia. The 10-min of exposure to the anaesthetics had no effect on the haematological profile of vimba bream. The effect of anaesthetics on biochemical indices of blood plasma was demonstrated. The exposure of the anaesthetics 2-phenoxyethanol and Propiscin influenced levels of glucose, ammonia and the activity of aspartate aminotransferase compared with the control group. The level of triacylglycerols and the activity of lactate dehydrogenase was affected to exposure of MS 222. Based on the results only clove oil had no effect on the haematological and blood biochemical profiles. Other anaesthetics tested more or less affect value of blood biochemical profiles.

The theoretical part of the thesis contains a literature review of the current knowledge on the occurrence and importance of aquatic invertebrates in salmonid fish farms. The practical part includes monitoring and determination of abundance, diversity and taxonomic composition of aquatic invertebrates in a recirculating system in Pravíkov. Sampling was conducted once a month during the vegetative season over three years, from 2015 to 2017. Samples were taken using an adjusted benthic net, from three sam-pling sites: bottom of the outflow canal from the breeding tanks, bottom of the inflow canal to the breeding tanks and the system’s wall. In addition to the abundance and diversity of aquatic invertebrates, the physico-chemical parameters of water were also measured. During the monitoring period, common breeding interventions were conduct-ed, including the discharge and disinfection of the entire system. During the monitoring period, a total of 36,066 individuals from 133 taxa of aquatic invertebrates were recorded. In 2016, despite the disinfection of the system, the highest number of taxa (74) and abundance (17,700) were registered. In 2016 and 2017, the vast majority of the macrozoobenthos collected were Chironomidae and Oligochaeta, which showed a significant growth in abundance in comparison with 2015. In 2015, 69 taxa with an abundance of 15,436 individuals were recorded. The cleaning of the system showed the highest effect on macrozoobenthos in 2017, when the bryophyte vegetation regrowth did not occur on the wall and some of the samples were without macrozoobenthos. Altogether, only 2,930 aquatic invertebrates and 67 taxa were detected. Values of the Shannon–Weaver index (H´) ranged from 1.335 to 2.214 in 2015, from 0.853 to 2.583 in 2016 and from 1.116 to 2.508 in 2017. Off all macrozoobenthos taxa recorded, Asellus aquaticus presents a potential danger to farmed fish, as it can be an intermediate host of Acanthocephala. This is also true for some species of molluscs, which can be intermediate hosts of trematodes.

This thesis provides an improve to existing reproduction technics through investigation of ecology and physiology features of pikeperch broodstock: (I) Spawning behavior and selectivity to different types of spawning substrates as an important part of the biology of pikeperch species. The main output of the study was revealing of strong selectivity to the spawning site with neither water temperature nor availability of spawning places haven't affected substrate preference of pikeperch broodstock. (II) Spawning in captivity is leads to decrease in physiological status of the pikeperch broodstock, especially in females. It was found that one of the reasons of the decrease was male protective behavior, that in limited space of the reproduction unit is forwarded to female. Separation of the sexes significantly reduces number injuries and improved physiological status of the broodstock. (Ill) The study investigated efficiency of different antifungal agents for pikeperch broodstock. The long term exposure to salt bath in concentration of 2.5, 5 and 10 g L-1 and formaldehyde in concentration 0.015 ml L-1 were found to be highly effective and significantly decreased mortality after spawning. In addition, treatment with salt bath are environmentally friendly and recommended for practical use as an effective way to prevent mortality of pond-cultured pikeperch broodstock. (lV) The provision of live feed is crucially important for proper gametes maturation, particularly in pond-cultured fishes not accepting pellets. The study investigated the effect of temperature on daily biomass of prey consumed by pikeperch broodstock. Significantly increased prey consumption was found after temperature reached 4.5 °C. Females exhibited significantly higher prey consumption rate in compare to male. Study revealed the tendency for pikeperch to consume largest available prey after water temperature reached 8.5 °C.

The aim of the thesis was to verify use of peracetic acid (PAA) in production conditions for ectoparasites control in carp pond farming. First test was about evaluation of organic load in pond water on speed PAA decay in two temperature regime (11 15 and 21 °C). Results showed that between 3 6 hours from PAA application the concentration of PAA was under a half of the initial concentration (6 mg.l-1). Also statically important differences (p= < 0.05) were found in speed of decay between samples with organic load (3 samples from ponds) and samples without organic load (distilled and tap water) in both temperature regimes. Application of PAA during the transport of fish into the transport boxes was performed in three age categories (1, 2 and 3 years old common carps), where the fish were exposed for 60 90 minutes in 1.5 mg.l-1 PAA as Persteril 36. Parasitic examinations of skin and gills showed reduction of number protozoal parasites (Trichodina spp. and Apiosoma spp.) in individuals comparing with control. Against other detected parasites was PAA ineffective. Statistical evaluation showed significant (p= <0.05) decrease in prevalence only in 3 cases out of 19 in total. Long-term four days long fish bath of carps which were heavily infested by Saprolegnia parasitica in 1.5 mg.l-1 PAA an positive effect on the overall survival was found. In the control group mortality reached 100 % the third day of trial, in contrast with treated group where was Saprolegnia parasitica succesfuly eliminated and overall moratily was 40 %. Continual fourteen days long application of PAA by peristaltic pump did not proved.

Angl. resumé

The aim of this diploma thesis was to elaborate the overview of applied strategies in salmonid rearing under the conditions of intensive aquaculture systems and to evaluate their production effect. Two feeding tests run within the NAZV program QJ1210013. The first feeding test was carried out from 15th May to 12th June 2014 in the Department of Fisheries and Hydrobiology, MENDELU. For this feeding test monosex female population of rainbow trout (Oncorhynchus mykiss) was included. Two types of dry food were administered ALLER AQUA -- ALLER SILVER and BioMar -- INICIO 918. The second feeding test was carried out from 11th June to 3rd September in the salmon farm in Pravíkov (BioFish company). To this feeding test, crossbreeds of brook trout (Salvelinus fontinalis) and arctic char (Salvelinus alpinus) were included. Two types of dry food were administered ALLER AQUA -- ALLER GOLD and BioMar -- EFICO ENVIRO 920. The length-weight parameters of individual fish were measured at the beginning and at the end of tests. The amount of administered feeds was recorded. Also basic physico-chemical properties of water were monitored. At the end of these tests the production (FCR, SGR, PER, etc.) and economy parameters were evaluated. The most favourable FCR (0,63) was achieved in the crossbreeds of brook trout and arctic char fed by ALLER GOLD. The most rapid growth of fish (SGR = 3,68) was achieved in the fish of monosex female population of rainbow trout fed by INICIO 918. The greatest yield (3 700 CZK per 1m3 of water) was achieved in crossbreeds of brook trout and arctic char fed by EFICO ENVIRO 920, when fed costs were 1 487 CZK per 1m3.