Dependence of linear growth and survival of larvae of the oriental river prawn (Мacrobrachium nipponense De Haan, 1849) on temperature and salinity

Purpose. Studies of the growth and survival of Oriental river prawn (Macrobrachium nipponense) larvae depending on water temperature and salinity during cultivation. Methodology. Experimental studies were carried out at the Aquatic Department of Aquatic Bioresources and Aquaculture of the Odesa State Ecological University in 2020-2021. Brood Oriental river prawns (Macrobrachium nipponense) were caught in the lower Dniester river and placed into a 0.8 m3 RAS. The larvae were stocked in separate aquariums with automatically maintained specified temperature regime. The first series of experiments in fresh water investigated the influence of water temperatures of 20–22, 22–24, 24–26, and 28–31 ℃ on the growth of shrimp larvae (from the 1st stage to the Pl stage). Findings. It was established that at a temperature of 24–26 ℃, the duration of the transition from one stage of larval development to another in Oriental river prawn (Macrobrachium nipponense) increased as the larvae grew and developed. It lasted 4–5 days in the first stages (1-3), then stages from 6 to 9 days in the later stages. High temperature stimulated the growth of larvae and accelerated their development. In fresh water at a temperature of 29–31 ℃, the length of postlarvae (Pl) reached 6.69±1.15 mm in 28 days of rearing. Cultivation at high temperature resulted in a significant variation in larval sizes (from 4.4 to 8.6 mm CV–25,27). At lower temperatures (25-27, 22-24 and 20-22 ℃), the average sizes of prawn postlarvae were smaller (5.83±0.78, 4.56±0.15, 4.43±0.15), and the survival rates increased (46, 49 and 54%, respectively). Survival of larvae was inversely dependent on temperature r = –0.89. It was minimal (32%) at a temperature of 29–31 ℃. The higher the growing temperature, the lower the output of postlarvae. Water salinity, like temperature, significantly affected the growth, survival and size uniformity of postlarvae. In water with a salinity of 5‰, postlarvae reached their maximum length (6.56±0.15 mm) at a temperature of 29-31 ℃. At temperatures of 20-22 and 22-24 ℃, the size of the postlarvae did not reliably differ among themselves. The maximum survival of postlarvae (52%) was noted at a temperature of 22-24 ℃. Regardless of water temperature, salinity of 5‰ ensured high uniformity of larvae size (CV: 6.11–9.09). At a salinity of 7‰, the maximum length of postlarvae was reached at a temperature of 29-31 ℃, and the highest survival rate of prelarvae (34%) was noted at a temperature of 20-22 ℃. The size of the larvae and their survival at other growing temperature conditions did not differ significantly (Р<95). A salinity of 7‰ also ensured the uniformity of postlarvae sizes (CV: 6.12-8.97). At a salinity of 12‰, high water temperature stimulated the growth of larvae with relative uniformity of their linear sizes, but in all variants of the experiment the survival rate of postlarvae was very low (4–9%). Originality. Experimental data on the growth and survival of larvae of the Oriental river prawn (Macrobrachium nipponense) depending on temperature and salinity are presented for the first time. The influence of the salinity of the environment on the size uniformity of the larvae was established. Practical value. The obtained results can be used for the development and improvement of methods of artificial reproduction and cultivation of the Oriental river prawn (Macrobrachium nipponense) under controlled conditions in recirculation aquaculture systems (RAS).