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Výhody a další perspektivy využití smíšené obsádky pstruha duhového (Oncorhynchus mykiss) a mníka jednovousého (Lota lota) v podmínkách intenzivní akvakultury
PROFANT, Vít
This diploma thesis was focused on the culture of rainbow trout (Oncorhynchus mykiss) in combination with burbot (Lota lota) in the Recirculation Aquaculture System (RAS). Production growth indicators, the amount of accumulated undissolved substances and their chemical analysis were compared. In addition, indexes, biochemical analysis and oxidative stress were compared between the experimental groups of burbot. Three groups were tested in the three repetitions. The first experimental group (70/30) contained 70 pieces of trout and 30 pieces of burbot, in the second group (85/15) there were 85 pieces of trout and 15 pieces of burbot and in the last third group (100/0) there were 100 pieces of trout and 0 pieces burbot. The experiment lasted 77 days and control overfishing and weighing, including collection of accumulated undissolved substances, took place on days 21, 42, 63, and 77, when the experiment was terminated. At the beginning and at the end of the experiment, the total length (TL), standard length (SL) and weight (W) were measured for both species. The average water temperature was 17, 91 ? 0.48 ° C and the light period was 12L: 12D, with an average light intensity of 150 lux. Almost no mortality was reported for rainbow trout, but for burbot the mortality was 10% in the group (70/30) and 24.4% in the group (85/15). The SGR for rainbow trout was the significantly highest in the group 70/30 in I. and II. experiment period. The FCR value occurred at the end of IV. period to decrease 0.2 in group 70/30 compared to group 100/0, but there was no statistical difference. Based on data from this experiment regarding biomass and weight of individual fish, rainbow trout has clearly outgrown burbot across all periods. The same result was seen for TL, SL, W and Fulton's condition factor (FC). In the group (70/30), the amount of accumulated undissolved substances in one day was statistically significantly reduced at the end of III. and IV. experiment period. The same result was obtained for the relative amount of undissolved substances in relation to the feed ration used. According to the chemical analysis of the collected undissolved substances, there was a significant reduction in the absolute amount of dry matter and organic dry matter in IV. experimental period. The reduction of the absolute amount of phosphorus and the improvement of its retention based on the relative amount of total phosphorus in the undissolved substances with respect to the amount of feed was confirmed at the end of III. and IV. period in group 70/30. 93 There were significant differences in burbot between groups 70/30 and 85/15 in spleen somatic index, oxidative stress in the intestine, and phosphorus levels in blood plasma. These values were higher in burbot in the group (70/30), indicating that burbot in this group were more limited by the food source. According to the mentioned results, the 70/30 group was considered like the most advantageous in comparison with the other tested groups with regarding to the amount of collected undissolved substances and nutrient retention. On the other hand, in terms of welfare and physiological condition of the burbot, the 85/15 group was better evaluated compared to the 70/30 group. In general, burbot can be considered as a new potential species according to this testing in order to more diversify of freshwater aquaculture.
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Vliv syntetických progestinů na vývoj gonád kapra obecného
PROFANT, Vít
This paper was focused on effect of synthetic progestins on gonadal development in fish. A 160-day chronic test on common carp (Cyprinus carpio), was run underlaboratory conditions. The fish was divided into five experimental groups. The first control group included clear diluted water without any occurrence of progestins. The second control group was kept in diluted water with dissolving agent DMSO (dimethylsulfoxide). The third group of fish was exposed to gestogene at a concentration level of 2 ng.l-1 and the fourth group was exposed to drospirenone at a concentration level of 2 ng.l-1. The last group (Mix) was exposed to gestogene and drospirenone simultaneously, where both substances corresponded to the concentration of 2 ng.l-1. The experimental groups were dosed with progestins dissolved in DMSO, since they have lipophilic nature. The determination of the influence of synthetic progestins on the gonadal development was based on histological examination of the exposed fish samples in toto. There was any signifficant difference in fish sex ratio and in percentage of intersex occurrence between the groups that wwere exposed to individual synthetic progestins and the control groups. However, the exposure of the mixture of drospirenone and gestogene (Mix) showed a significant difference. Primarily, a high percentage of intersex was detected with the number reaching 36.6 %. The occurrence of intersex suggested a twist in sex of exposed fish through ontogenesis.
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