To the question of rearing brood sterlet (Acipenser ruthenus Linnaеus, 1758) in floating cages at natural water temperatures of the forest-steppe of Ukraine

Purpose. To study environmental conditions and individual fish culture parameters in the process of rearing brood sterlet herders in cages at natural temperature regime of water bodies of the forest-steppe zone of Ukraine. Methodology. The material for the study were age-1–7 groups of sterlet reared in floating cages with areas of 24 m2. Fish were fed by specialized feeds with the content of crude protein of 45–64% and raw fat of ― 12–15%. The individual and mean body weight (g), relative weight gain (%) and fish survival rate (%) were studied; fish production per unit area of cages (kg/m2) and feed costs per unit weight gain (kg/kg) were calculated). The determination of the physical and chemical parameters of the environment was carried out using generally accepted methods in fish culture and hydrochemistry. Findings. The mean monthly water temperature was in the range of 21.7–26.3°C in the summer. The period with a water temperature of 18–25°C was 75-80 days. The mean daily content of dissolved oxygen varied within the range of 2.4–11.6 mgO2/dm3. The mean monthly oxygen concentration in summer was between 3.7 and 6.2 mgO2/dm3. During the period of fish rearing, minor excesses of normative values ​​have been recorded for some hydrochemical parameters. No mass manifestations of fish diseases were detected. It was established that feed costs per unit of body weight gain (kg) increased with fish age, on average, from 1.29 to 1.98 kg. Fish production in cages was 5.33–11.35 kg/m2. On the seventh year of life, the brood sterlet reached a mean weight of 1796.80 ± 73.33 g (Cv = 20.4%). Survival rates for sterlet of different age groups were 78.50–98.96%. The number of sterlet for the organization of caviar and meat production was calculated. Originality. Peculiarities of rearing different age groups of sterlet with the use of the methods of industrial aquaculture uncommon in Ukraine under conditions of cage aquaculture systems installed in water bodies with natural temperature regime have been investigated. Practical value. The results of the study are of interest for the development of modern methods of aquaculture of sturgeons in the conditions of farms of industrial type.