Assessment of the growth rate of juvenile Australian red-clawed crayfish Cherax quadricarinatus (von Martens, 1868)

Background. The study is devoted to the study of the main fish-breeding and biological characteristics (growth rates, survival, etc.) of juvenile Australian red-clawed crayfish Cherax quadricarinatus (von Martens, 1868) when kept in different temperature conditions. In the experiment, two temperature zones were compared: 22 °C (suboptimal conditions for commercial cultivation) and 26 °C (optimal conditions). The results showed that at a temperature of 22 °C, there was a higher increase in weight (18.03%) and length (4.19%) compared to suboptimal conditions (5.99% and 4.92%, respectively). The Fulton fatness ratio decreased in both groups. The data obtained is important for commercial aquaculture for the correct development of cultivation biotechnologies.

Purpose. The aim of the work was to study the main fish-breeding, biological and physiological parameters of juvenile C. quadricarinatus when they are kept in different temperature conditions.

Materials and methods. The study was conducted on 73-day-old C. quadricarinatus individuals (n=40), divided into 2 groups of 20 specimens each. in each. Group No. 1 was kept at a temperature of 22-23°C, group No. 2 – at 26-27°C. The specimens were placed in polypropylene containers with overall dimensions of 74x57x41 cm. Each tank had an individual recycled water filtration system. To reduce cannibalism, PVC pipe shelters were placed in the tank. The duration of the experiment was 28 days.

The main water parameters were monitored daily using specialized equipment and sets of test systems. Feeding was carried out twice a day: frozen chironomid larvae (50%) and young bean fruits (50%) in the amount of 6% of the biomass.

The body weight and length of each individual were measured every 7 days of the experiment. Based on the data obtained, the main fish-breeding and biological indicators (Fulton fatness coefficient, specific growth rate, survival rate) were calculated. Amino acid analysis was performed by capillary electrophoresis after acid/alkaline hydrolysis of muscle tissue. To minimize errors, averaged samples from individuals of different sizes were used.

Results. During the study, the hydrochemical regime corresponded to the optimal values for the content of C. quadricarinatus. The absence of toxic nitrogen compounds, as well as copper ions, made it possible to create the necessary conditions for the experiment. In group No. 1, the water temperature averaged 22.26 °C, and in group No. 2 – 26.96 °C. The concentration of dissolved oxygen (O2) during the experiment averaged 7.52 mg/l and 7.87 mg/l, respectively. As a result of the research, it was found that in group No. 1, the body weight of juveniles increased by 5.99%, length – by 4.92%, while the Fulton fatness coefficient decreased by 8.18%. In group No. 2, weight gain was more pronounced (18.03%), with a moderate increase in length (4.19%) and a smaller decrease in fatness ratio (4.1%). The analysis of the amino acid composition of muscle tissue revealed significant differences between the studied groups. The concentration of arginine in the muscles of juvenile crayfish from group 1 was significantly higher than in group 2. The total concentrations of glutamic acid and glutamine were also higher under suboptimal conditions. These changes most likely indicate metabolic adaptation to stressful conditions, especially at temperatures close to the lower optimal limit of the species. Thus, during the experiment, it was found that the water temperature of 26-27 °C contributes to higher growth rates and survival of juveniles, while 22-23 ° C causes changes in the physiological status of C. quadricarinatus.

Conclusion. The study revealed differences in the fish-biological and physiological parameters of C. quadricarinatus juveniles kept in different temperature conditions. At an average temperature of 26.96°C, the maximum increase in weight (18.03%) and body length (4.19%) was observed, while at 22.26°C these indicators were significantly lower (5.99% and 4.92%, respectively). Although the survival rate remained high (95-100%) in both cases, a decrease in the fatness coefficient by 8.18% at a lower temperature indicates the stress effect of this factor on the aquatic organisms. Amino acid analysis showed an increased content of arginine (5.315%) and glutamic acid (4.221%) in individuals kept at a temperature of 22-23 ° C, which indicates the activation of compensatory metabolic mechanisms. These data probably indicate the high possible adaptability of the species in question to changing environmental conditions. The results obtained are of great practical importance for the further development of crustacean aquaculture (astaculture) in the climatic conditions of the Russian Federation.