Efficiency of growing sturgeon (Acipenseridae) fish species juveniles under different water hardness

Purpose. To evaluate the influence of water hardness on productive parameters when growing sterlet and Russian sturgeon juveniles to viable stages as well as on the formation of the leukocyte formula.indings. A difference in the results of growing sterlet and Russian sturgeon in water with experimentally created different hardness has been shown. It was found that the optimal environment for growing sterlet is water with a hardness of 4.0 mg-eq/dm3. After 14 days of growing, the average weight of sterlet grown in this water was 1.3 times higher than in the experimental group of fish No. 3, and 2.1 times higher than in the experimental group compared to group of fish No. 1. After 21 days of the experiment, the growth trend was maintained: the average weight of the fish of this group was 1.5 times higher than that of the experimental groups No. 1 and No. 3. After 28 days of cultivation, the average weight of the sterlet in group No. 2 was 1840.00±0.210 mg, and was higher than in groups No. 3 and No. 1 by 1.8 and 1.4 times, respectively. Cumulative mortality in all sterlet groups during the experiment ranged from 8.00 to 11.00%. No significant difference in this parameter was found between the groups, although the tendency towards increased vitality was preserved in group No. 2. Analysis of blood smears after 28 days of cultivation showed a slight difference in the leukogram of the experimental groups. In the peripheral blood of experimental group No. 1 during 21 days of cultivation in “very soft” water (2.5 mg-eq/dm3), a 15% higher count of immature lymphocytes was found than in groups No. 2 and No. 3. Also, in group No. 2 there was a tendency to increase the count of erythroid cells. It has been found that in juvenile starlet grown in “very soft” water, the differentiation of cells of the lymphocytic line occurred a little longer, which was evidenced by the presence of a higher number of lymphoblasts and prolymphocytes.Originality. The advisability of modeling the water environment with the appropriate hardness for rearing various sturgeon species depending on their halophilicity has been demonstrated. The development of the blood leukocyte pattern of sterlet and Russian sturgeon juveniles grown in water with different hardness has been described. Practical value. The obtained results will be useful for improving the technology of early rearing of sturgeon larvae and fry. The application of the acquired knowledge will allow reducing mortality during the critical periods of their cultivation and will allow strengthening the non-specific immunity of these valuable fish species. Keywords: sturgeon, water hardness, viability, leukocyte formula.