Monitoring of hydrochemical parameters of the recirculating aquasystem in the early stages of ontogeny of Acipenser Ruthenus
Abstract
The technological process of reproduction and rearing of Acipenser Ruthenus, juveniles and older age groups, in industrial fish farms is carried out in recirculating aquaculture systems with constant monitoring of the hydrochemical regime of the aquatic environment and strict adherence to the technology of phased feeding with live and artificial feed. Raising sturgeon species in winter at low temperatures (2–6 ºС) is one of the most difficult technological processes. The selection of Acipenser Ruthenus fry was carried out in February 2024 at a water temperature of 4 °C and gradually increased by 0.5 °C per day for 20 days to prevent a sharp increase, which could provoke active mobility and exhaustion, injury, and weight loss. The water temperature in the pools and trays of the experimental farm fluctuated between 4 and 18 °C during February – March 2024, which corresponds to the generally accepted temperature range for reproduction and rearing of Acipenser Ruthenus. Compliance with the temperature regime and control of the dissolved oxygen content in water directly affects the survival, growth rate and feed consumption efficiency of Acipenser Ruthenus juveniles at juvenile stages of development. Water turbidity is the only indicator that does not comply with GOST 3351-74 and ranged from 1.12–1.53 mg/dm3 with a norm of ≤ 1 mg/dm3, which is 0.01–0.02 % higher than the norm and indicates the ingress of a small amount of meltwater and rainwater runoff into groundwater. Exceeding the norm of turbidity can adversely affect the vital activity of aquatic organisms in recirculating aquaculture systems and affect body weight gain because suspended particles settle on the gills of fish and impair their respiration, food consumption and ionic metabolism. The presence of chlorides of organic origin in water indicates its contamination, but in the studied water samples its content ranged from 14.18–16.31 mg/dm3, which does not exceed the norm according to the Sanitary and Epidemiological Standards. The lack of oxygen in water can affect the accumulation of hydrogen sulfide as a result of the reduction of sulfuric salts and, as a result, lead to an increase in the content of sulfates, but in our case, the hydrochemical analysis of the water samples under study shows that the sulfate content does not exceed the norm and is 13–52.6 mg/dm3. To organise a balanced feeding of young Acipenser ruthenus at this industrial farm, Artemia salina is used as live feed. To obtain live fodder, we incubated pre-prepared Artemia salina eggs, which allows us to obtain a complete feed for feeding Acipenser ruthenus juveniles in a short time. The decontamination of Artemia salina eggs was carried out in incubation devices (with mandatory aeration, which ensures the absence of anaerobic zones in the egg mass and intensive lighting. For incubation, a solution of 50 g (5 % w/v) of sodium chloride (NaCI) per 1 litre of water is prepared, into which eggs are loaded at a density of 5 g/L. For one apparatus, load 10 litres of water and 50 g of Artemia salina eggs. The incubation lasts 24 hours at a water temperature of 27–29 °C. The yield of Artemia salina nauplii from one device is about 80 %.
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