Water quality and growth performance of Litopenaeus vannamei at different stocking densities in a chemoautotrophic-based system with limited organic carbon supplementation during the nursery phase

Water quality and growth of Litopenaeus vannamei were monitored at different stocking densities in a zero-water exchange nursery system inoculated with chemoautotrophic bacteria and limited organic carbon (OC) addition. Shrimp (similar to 3.4 mg) were divided into four groups of 200 PL/m(2) (T200), 500 PL/m(2 )(T500), 1000 PL/m(2) (T1000), and 1500 PL/m(2) (T1500). At the end of the study, the water temperature, pH, salinity, dissolved oxygen, oxidation-reduction potential, and dissolved oxygen saturation were within the optimal range. Total dissolved solids and electrical conductivity were lower in T200. The highest concentrations of free CO2 were observed in T1500. The results also revealed higher levels of alkalinity in T1500 compared to T500 and T1000. Notably, TAN was lower in T200 than in T1000 and T1500. Nitrite nitrogen (nitrite-N) and nitrate nitrogen were also lower in T200. Furthermore, TAN and nitrite-N levels rapidly elevated upon OC addition. Interestingly, nitrite-N levels exhibited a decrease whenever OC application was terminated. Total heterotrophic and Vibrio sp. bacteria in water samples were not affected by study groups. Regarding growth performance, T200 had significantly better final weight, weight gain, specific growth rate, and weekly growth rate. However, T1500 had the highest shrimp yield (kg/m3 or kg/m(2)). In conclusion, OC in the chemoautotrophic system interferes with the nitrification cycle, disrupts the effective conversion of nitrogen, and leads to further deterioration of water quality and shrimp growth performance at higher stocking densities. In this system, shrimp at the lowest density (200 PL/m(2)) reached the highest final weight and survival.