Survival of white shrimp Litopenaeus vannamei poslarvae at different salinities and temperatures

Objective. The combined effect of salinity (5, 15, 25, 35, and 45psu) and temperature (15, 20, 25, 30, and 35°C) was evaluated on survival and molt frequency in Litopenaeus vannamei postlarvae (PL12). Materials and methods. Four repetitions were applied to each combination of salinity and temperature. The PL were placed in 3 L beakers at a density of 100PL/l. Salinity was increased by dissolving commercial salt without iodine, into marine water, whereas fresh filtered tap water was used to decrease the salinity from seawater. The PL were adapted at 35psu and 28°C (initial conditions) during 30 minutes. Thereafter, they were transferred to each experimental combination of salinity and temperature by 30 minutes. Following this procedure, the PL were filtered and retuned to their initial acclimatization conditions. After 30 minutes of recuperation, the live PL and molts were counted. All data were analyzed using a two-way ANOVA. Results. Survival and molt frequency were significantly (p<0.05) affected by salinity, temperature and the interaction of both factors. The maximum and minimum survival rates of 99.8 and 94.4% were obtained. Survival and molt frequency rates were significantly (p<0.05) affected by salinity, temperature and the interaction of both factors. Survival and molt frequency percentage rates decreased at lower salinity in combination with lowest and highest temperatures, and significantly increased, independently from salinity and temperature conditions, with exception of 5psu at 15, 30 and 35°C. The highest mortality rate (5.6%) was obtained at 5psu and 30°C. Conclusions. It was determined that survival of postlarvae was higher at temperatures of 20 and 25°C given salinity combination, which are considered the best conditions for survival and resistance.