Аңдатпа
The purpose of the work: to study the effect of water with different sodium chloride content on the main biological parameters of the juvenile Australian red-clawed crayfish Cherax quadricarinatus. Methods used: when performing experimental work for 30 days, the main biological characteristics of juvenile C. quadricarinatus with an initial mass of 0.64±0.27 g and a length of 31±5 mm were determined when it was grown in water with a sodium chloride content of 0, 5, 10 and 15 g/l and controlled the survival, growth, physiological state of individuals. Novelty: the novelty elements of the presented study are the identification of the negative effect of water with a sodium chloride concentration of 5–15 g/l on survival, size, mass and physiological characteristics of juveniles. Result: the survival rate of the studied juveniles on the 30th day of the experiment in fresh water was 65%. In water with a sodium chloride content of 5 g/l, the indicator was significantly lower — 23.3%. In the variants of the experiment with higher salt concentrations (10.15 g/l NaCl), by the 20th day all individuals died. The average weight of individuals (1.70±0.80 g) in the control group increased by an average of 166% from the baseline (0.64±0.27 g). Lower mass values were obtained at a salt content of 5 g/l — 1.00±0.49 g. This result was significantly (p<0.05) lower by 41% than in the control group. During the experiment, the average length of individuals (43±8 mm) in the control group increased by an average of 39% from the original (31±5.0 mm). The concentration of hemocyanin in juveniles contained in water with a salinity of 5 g/l is lower than in the control group by 16%. External signs of the development of rust-spotted disease have been identified. Practical significance: the results obtained can be used in the cultivation of the C. quadricarinatus. It is considered acceptable to keep crayfish juveniles in water with a sodium chloride concentration of not more than 5 g/l for 10 days. Keywords: crustaceans, Cherax quadricarinatus, juvenile, hemolymph, hemocyanin, sodium chloride, melanization, fungal disease>˂ 0.05) lower by 41% than in the control group. During the experiment, the average length of individuals (43±8 mm) in the control group increased by an average of 39% from the original (31±5.0 mm). The concentration of hemocyanin in juveniles contained in water with a salinity of 5 g/l is lower than in the control group by 16%. External signs of the development of rust-spotted disease have been identified. Practical significance: the results obtained can be used in the cultivation of the C. quadricarinatus. It is considered acceptable to keep crayfish juveniles in water with a sodium chloride concentration of not more than 5 g/l for 10 days.