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Vliv délky a způsobu transportu jiker na jejich líhnivost u hlavatky obecné (Hucho hucho)
BERÁNEK, Lukáš
The success of transporting both unfertilized and fertilized artificially stripped ova of huchen from the farm for up to 5 days was tested. A mixture of ova from 8 females was divided into two parts. The first part was inseminated with artificially stripped sperm (a mixture from several males) on-site (1 hour after stripping), and after rinsing the fertilized ova with water, it was placed in water in a plastic sealable container. The second part of the ova, along with the ovarian fluid, was not inseminated with sperm and was placed in another identical container. Both containers were stored in a thermal insulation box for the following 5 days, including transportation from the site of artificial stripping to the incubation site. The mixture of collected sperm from 5 males was stored in syringes in a separate isothermal box at a temperature of +4°C. Both thermal insulation boxes were placed in the luggage compartment of a passenger car for 5 days. For the ova transported in water, the water was exchanged twice a day. Throughout the first day, both the ova and sperm were transported from the site of artificial stripping to a distance of 350 km to the incubation site. In the following days, the car was driven three times a day for at least 0.5 hour each time to simulate vibrations occurring during transportation. The ambient temperature for the ova during transportation was maintained at 10°C. Samples of both fertilized and unfertilized ova were taken at one-day intervals from the artificial stripping, and after counting and fertilization of the ova with transported sperm, they were rinsed and placed in small incubation dishes with separate water inflows and perforations allowing water flow and preventing the escape of subsequently hatched embryos. Thirty ova were always placed in each variant, with 3 repetitions in all variants. The incubation dishes were placed on the bottom of a shallow flow-through channel supplied with water from a recirculating system with cold-water fish farming. The average water temperature during incubation was 12.8°C. Mortality of the ova was monitored during incubation, white unfertilized or dead ova were removed, and hatching of the embryos was recorded. In the first variant, after stripping the fertilized ova transported in water for one, two, or three days, a hatchability of 32.2 ? 21.1%, 27.8 ? 10.3%, and 33.3 ? 32.1%, respectively, was achieved. After simulated transportation for four and five days, the hatchability decreased to 21.1 ? 1.57% and 15.6 ? 8.3%, respectively. The differences between all the aforementioned parameters are not statistically significant. In the second variant, with unfertilized ova transported in ovarian fluid, a comparable hatchability (34.4 ? 11%) was achieved after one day of transportation, as with fertilized ova transported in water for one to three days. Unfertilized ova transported in ovarian fluid for a longer period (two and three days) showed a statistically significant decrease in hatchability to 7.8 ? 8.8% and 2.2 ? 1.6%, respectively. A 100% mortality rate was found for ova transported in unfertilized ovarian fluid for four and five days. No differences were found in the length of the incubation period due to different methods or lengths of ova transportation. The experiment demonstrated the feasibility of using transportation of fertilized ova in water for several days, with transportation of fertilized ova in the aquatic environment being preferable.
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