Peculiarities of cultivation of Siberian sturgeon (Acipenser baerii Brandt, 1869) breeders using floating cages in the climatic conditions of the forest steppe of Ukraine

Purpose. Study of the technological processes and results of the cultivation of Siberian sturgeon (Acipenser baerii) in floating cages at the natural water temperature of the forest-steppe of Ukraine to ensure caviar production. Methodology. The study was conducted in the conditions of the cage area of the industrial-type farm (limited liability company - the agricultural aquaculture enterprise “Osetr”) located in the right-bank part of the Kaniv Reservoir on the Dnipro River. Different age groups of sturgeon were grown in floating cages with an area of 24 m2 (4×6 m). The walls of the cages were submerged in water for 2.5–3.0 m. Depending on the fish age, cages with mesh sizes of 10–24 mm were used. Fish of different ages were fed at a water temperature not lower than 5.5–6.0°C with compound feed containing 45–52% crude protein and 12–15% crude fat. Individual and average body weight (g, kg), relative and absolute annual weight gains (%, kg) and fish survival rate (%) were determined. The amount of fish yield per unit area of cages (kg/m2) and the average daily consumption of feed per average body weight of fish (%) were calculated. The study of productive parameters and physicochemical factors of water was carried out according to generally accepted methods in ichthyology and hydrochemistry. Findings. Average monthly values of water temperature in the summer season during 2018–2023 were within 20.9–25.3°C. The period with a water temperature of 15–25°C did not exceed 160 days. The duration of the fish feeding period was 225–260 days. The dissolved oxygen content in the summer ranged from 3.8 to 9.4 mg O2/dm3. Average seasonal oxygen concentration in water were in the range of 5.8–6.3 mg O2/dm3. During the cultivation of different age groups of sturgeon, periodic moderate exceedances of the normative values for certain hydrochemical parameters were registered. No mass death of fish was detected. Feed consumption per day, depending on the age of the sturgeon, was on average within 0.7–2.5% of the fish weight. The average seasonal gains of age-1+ to age-10+ sturgeon were in the range of 0.47–1.11 kg, with maximum values for age-3+ fish. The average weight of age-10+ sturgeon reached 6.8 kg. High survival rates of fish of various ages were recorded (93.5–100.0%). The fish yield of cages with different age groups of sturgeon were 5.7-12.9 kg/m2. Originality. Peculiarities of the formation of the brood stock of Siberian sturgeon with the use of floating cages installed in a reservoir with natural water temperature of the forest-steppe of Ukraine for caviar production were studied. Practical value. The results of the study are of interest for the development of the sturgeon caviar aquaculture in Ukraine in the conditions of industrial-type farms, primarily using water bodies with a natural temperature regime.