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Umělý výtěr karase obecného
VRBENSKÝ, Jakub
The thesis briefly summarizes the available information in the field of crucian carp biology. The experimental part includes, firstly, monitoring the effect of water temperature during the latency period in reproductive females affects the success of artificial spawning, the survival of eggs to the eyespot stage, the length of the latency interval in hours and in clock degrees, the relative fecundity of reproductive females and the pGSI. In the second part of the experiment, secondly, the effect of the method of unstickness eggs on the survival of eggs to the eyespot stage. To test the effect of temperature during the latency interval, the females (mean weight 329 +- 60 g) were divided into 7 groups (n = 5). The individual groups of reproductive females were placed in separate tanks with average water temperatures of 15.4, 17.2, 18.9, 21, 23.2, 25.2 and 27.2 °C. Females and males were injected with the hormone Ovopel (1 pellet per 1 kg of fish). Before injection and artificial spawning, the reproductive fish were anaesthetized with clove oil (0.03 ml.l-1). The each group of females were artificially spawned, the eggs were seeded with a mixture of sperm from three males, activated with hatchery water and unsticked with cow's milk diluted with water (1:9). Incubation of eggs was carried out in small experimental Zug bottles (0.45 l) at an average temperature of 21 °C. The highest number of ovulated and artificially spawned females was found at temperatures of 21 - 25 °C (80 %). At lower and higher temperatures the success of spawning was lower. A close positive linear dependence of the latency interval length (in hours) on water temperature was found in the monitored range of 15.5 - 27.2 °C (y =-1.5062 x + 50.663; R2 = 0.924). The length of the latency interval at 21 and 23 °C was 18,4 +- 0,9 and 12,4 +- 0,2 h, respectively 387 +- 18 and 289 +- 5 h°. The eggs have a yellow-brown to green-brown colouration, the average weight of one unswollen eggs is 1,10 +- 0,07 mg (corresponding to 911 +- 51 thousand eggs in 1 kg of eggs). In contact with water, the eggs are very sticky. The highest relative working fecundity was achieved at 21 and 23 °C (71,9 +- 10 and 75,9 +- 34 thousand eggs per 1 kg of female). The average survival rate of eggs to the eyespot, originating from artificially spawned females kept during the latency interval at temperatures between 18,9 - 23,2 °C, ranged from 92.9 +- 0.5 to 99.6 +- 2.2 %, and was lower at 17.2 and 27.2 °C (86.2 +- 0.6 respectively 74.2 +- 3 %), differences between groups were statistically significant. In evaluating the effect of unsticking preparations on the survival of eggs to the eyespots, the highest survival was achieved with milk (71.9 +- 7.3 %). Statistically conclusively lower survival was found with tannin (47.4 +- 0.4 %) and acetylcysteine (48.4 +- 8.6 %). The achieved results can be used in artificial spawning of crucian carp as part of rescue breeding.
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Comparison of different ways of breeding, nutrition and controlled reproduction of Lota lota
ZÁVORKA, Milan
Based on the results reached after 216 days of experimentation with various breeding types, it can be said that the type of feed is not of paramount importance. This fact is based on the previous adaptation of submitted food, this is especially important for artificial feed. From our point of view, the more important factor is temperature, intensity and method of breeding. Prey selections choices involving 11 species of fish were performed on age groups of different burbot. All groups of burbot preferred the following species: grass carp, pikeperch, tench and stone moroko. The non-preferred species was ruffe. And different preferences were set for common carp, silver carp, burbot, sunfish and also for roach. The study evaluated reproductive parameters in burbot (Lota lota ) and focused on incubation time in two localities. Burbot spawning was observed from January to early February at an average temperature of 1.55 +- 0.9 °C in Borova Lada and 4.78 +- 0.11 °C in Mydlovary. For burbot at the age of 2+, at an average 1166 +- 100 were determined number of swollen eggs per gram. Relative fecundity was at 257260 +- 70678 eggs per kilogram of female. The absolute fecundity was at 24232 +- 6753 eggs.The last parameter evaluated was the incubation period. The average incubation period in the years 2020-2022 was 202 +- 24.55 °D in Mydlovary and 75.8 +- 16.67 °D in Borova Lada. In connection with artificial spawning, in this study, we further point out the possibility of peeling artificially spawn eggs with NaClO, in which we did not observe a negative effect.
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