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Vliv teploty na schopnost oplození a líhnivosti při krátkodobém skladování neoplozených jiker síha peledě (Coregonus peled)
RYTÍŘ, Jan
The northern whitefish Coregonus peled (Gmelin, 1788), originally from Russia, was introduced to the Czech Republic in 1970 for its tasty meat and good growth ability. Breeding of this species has been very popular in the past. Currently, thanks to the fish-eating predators, traditional breeding of this species is on decline. The aim of this M. Sc. Thesis was to sumarize the avaible information in the field of peled biology, artificial propagation and also information about effect of temperature on the ability of fertilization and hatching for short-term of unfertilized eggs in other salmonid species. In the practical part, the influence of temperature and length of storage of stripped, unfertilized eggs of peled on fertilization, survival to eyed eggs and hatching were observed. Unfertilized eggs were divided into five bowls and deposited in thermo boxes, which were tempered to 2.5, 5, 7.5, 10 and 12.5 °C. After time intervals of 1, 4, 12, 24, 36, 48, 60 and 72 hours, approximately 100 - 200 eggs were taken from each thermobox, which were fertilized with fresh sperm (collected from several males) and water from the hatchery. The fertilized and purified eggs were moved to the incubators with continuously inflow of fresh water. Dead eggs were removed and recorded. Subsequently, fertilization, eyed eggs and hatching eggs were determined. The resulting values of these parameters were expressed as a percentage of the total number of used eggs. High levels of fertilization and survival to eyed eggs were achieved when stored within 1 day from eggs stripping at all temperatures except the highest temperature of 12.5 ° C. As the interval gradually lengthened, the fertilization and survival parameters also decreased, most notably at 7.5 and 10 ° C. To obtain the largest possible amount of fry in fishing practice, it is recommended to store eggs at 2.5 and 5 ° C, up to 48 hours after ova stripping. At higher temperatures, the effective storage time is reduced to 12 hours. Storing eggs for longer than 48 hours, in practical terms has no meaning. At the same time, it was found that at the above-mentioned optimal temperatures for storing eggs (2.5 and 5 ° C), the best hatching results were obtained when storing stripped eggs for 12 hours. Not only for longer, but also for shorter storage lengths, the values of this parameter were lower.
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