Vliv teploty na udržení schopnosti oplození a líhnivosti při přechovávání neoplozených jiker u lína obecného

This theses deals with the storage length of artificially spawn of hard roes of Tench (Tinca tinca) during different temperatures at the time before the semen discharging and activation to fertilization, hatching and consequent survival of fish hatchery throughout changeover from the embryonic to larval life period (beginning of active food intake). Homogeneous assortment of hard roes obtained from hormonally induced artificial hatching of 6 spawners has been used for this experiment. Samples of hard roes were put into plastic bowls and covered, immediately after artificial hatching. Subsequently, they were placed into tempered, thermo-isolating containers with temperatures of 5, 10, 15, 20, 25 and 30 °C. In time intervals of 0.5; 1; 1,5; 2; 3; 4; 6; 8 and 10 hours, a small amount of hard roes were taken away from each temperature (estimated 50 -100 pieces) and put into dry, glass beakers (in 3 repetitions in each temperature combination and length of storage). Subsequently, the semen discharging from 6 milters was carried out and activation by water was performed. Incubation took place in non-sticking environment. During the incubation, or more precisely during the consequent storage of embryos through temperatures between 19-20.5 °C, water was changed daily. Fertilization was evaluated 48 hours after fertilizing. Hatchery was determined 48 hours after beginning of hatching of first specimen. After changeover from embryonic to larval period of ontogenetic development, living food was offered to hatching fish (artemia sp.). Thereafter, the amount of hatched fish with filled intestines was counted. Ascertained values were depicted as a percentage from the total number of seeded hard roes as well as fertilized hard roes with the use of statistic methods (two factors Anovy with the repetition). The highest level (in statistic evaluation on the importance level alfa = 0.05) of hard roe hatchery was accomplished throughout the length of possession and temperature 1 hour/ 25 °C (68.0 +- 3.1 %). The high level of hatchery was maintained by hard roes stored for 2 hours, afterwards a gradual value decrease was registered. Similarly, that was achieved with hatching parameter, where the high level of hatching was achieved with hard roes possessed for the period of 3 hours (except temperature of 30 °C), afterwards the hatchery was decreased. Pursued survival and food intake parameters of hatched fish (from the practical point of view) confirmed above stated dispositions. The high hatchery from placed hard roes was maintained for 1.5 - 3 hours (except 30 °C), thereafter there was its gradual decrease. In the time of 8 hours (temperatures 5 - 20 °C), the survival of 1.2 +- 1.8 %, was found out, with the rest, the survival was nearly zero