Response surface analysis of temperature-salinity interaction effects on water quality, growth and survival of shrimp Penaeus vannamei postlarvae raised in biofloc intensive nursery production

This study aimed to evaluate the effect of temperature-salinity interaction on physico-chemical parameters, plankton composition, performance growth, and survival of shrimp Penaeus vannamei raised in intensive nursery production with biofloc system and zero-water exchange, by means of the response surfaces analysis. A 3 x 3 factorial experiment was conducted to determine the effects of temperature (24, 28, and 32 degrees C) and salinity (10, 20, and 30 g L-1) on water quality, performance, growth, and survival of Penaeus vannamei with the initial wet body weight of 0.004 +/- 0.001 g. The experiment lasted for 4 weeks. The temperature and salinity, independent and their interaction, had a differential effect on the studied parameters. At higher temperatures, there was a significant tendency to increase the concentration of total ammonia-nitrogen, nitrite, nitrate, total suspended solid and sedimentable solid, and lower dissolved oxygen concentration was found. Chlorophyta and rotifers were the most dominant groups of phytoplankton and zooplankton in the studied biofloc, respectively. The results showed that all shrimp had survivals above 84.5% at temperatures of 24-28 degrees C. The survival decreased with increasing the temperature from 28 to 32 degrees C. All growth parameters increased with the increase of salinity in the 24-28 degrees C temperature range, reaching a maximum value at 32 degrees C and 20 g L-1. In contrast, FCR decreased in response to increasing temperature within the tested salinity. The results of the response surface methodology demonstrated the effects of temperature-salinity interaction on the growth and survival of the postlarvae and early juveniles of shrimp P. vannamei in the biofloc system. The optimum conditions to obtain the maximum specific surface area of final weight, feed conversion ratio, specific growth rate, weekly growth gain, productivity, and survival were temperature of 27.25 degrees C and salinity of 25.5 g L-1, which were derived from the optimization approach. The results of this study help illustrate the range of temperatures-salinity options of shrimp raised for intensive nursery production in commercial-scale biofloc systems.