OPTIMIZATION OF THE CONDITIONS OF STERLET (ACIPENSER RUTHENUS, L. 1758) SPERM CRYOPRESERVATION FOR EGG FERTILIZATION IN FISH FARM CONDITIONS

Purpose. To optimize the conditions of sterlet sperm cryopreservation for works on egg fertilization and for producing viable offspring in the conditions of sturgeon farms. To analyze the effect of sperm freezing in different forms on spermatozoa survival and egg fertilization. To compare the results of cryoprotective solutions with compositions on the results of their use of sterlet sperm fertilization and to analyze their effect on the quality of the produced offspring. Methodology. The task aimed at optimizing the conditions of sterlet sperm cryopreservation for egg fertilization in the conditions of fish farms were carried out according to generally accepted methods in cryobiology and recommendations of Ye.F. Kopeika. The works with the produced sterlet offspring were carried out according to conventional sturgeon culture methods. Findings. The studies showed that the optimization of the conditions of sterlet sperm cryopreservation allowed preserving the properties of thawed spermatozoa at the level of native sperm. It was found that the functions of the sperm cryopreserved in liquid nitrogen vapors in granules in solutions with methanol or dimethyl sulfoxide (DMSO) were better preserved in granules when using methanol. The functions of the sperm after its freezing in cryopreservation solutions №№ 5 and 6 were evaluated in the conditions of a fish farm. It was found that the fertilizing capacity of the cryopreserved sperm in the solution № 5 (85.6 %) (with lower osmolality) did not virtually differ from the control (87.6 %) when using 25-60 g of eggs. In the cryopreservation solution № 5, this value was 17.6 % lower. The weight and length gain after egg fertilization with the sperm cryopreserved in both solutions in 3-month fish was higher than in the control. Originality. Introduction of creatine and fructose into the cryopreservation solution allowed increasing its protective properties and preserving spermatozoa activity after thawing at the level of the native sperm. Sperm cryopreservation in granules allowed optimizing the conditions of low temperature freezing of this sturgeon species and producing high quality viable offspring. Practical value. The obtained results can be used by sturgeon culturists in the conditions of fish farms for works aimed at producing viable sterlet offspring both for commercial purposes and for restocking into natural water bodies as well as by cryobiologists for works with other fish species.