Performance of a photo-heterotrophic, hypersaline system for intensive cultivation of white leg shrimp (Litopenaeus vannamei) with minimal water replacement in lined ponds using a stochastic approach

Abstract

The aim of the study was to evaluate the performance of Litopenaeus vannamei in an intensive photo-heterotrophic hypersaline system with minimal seawater replacement, and establish relationships between parameters of a stochastic production model and relevant water quality variables. Six experimental 1000 m2 lined ponds were stocked at a density of 120 shrimp m−2 for a 105-day trial. Salinity increased from 37 to 45 ± 2 g/L, and the water level was maintained with the weekly addition of filtered seawater, equivalent to 1.6% per day. The stochastic model predicted that, at harvest, there is 95% confidence that the system produces between 12.1 and 14.7 t/ha with a mean final individual weight of 13.1 g and a mean survival of 84.2%. Sensitivity analyses showed that dissolved oxygen and individual final weight of shrimp were the main variables influencing yield variance. Nitrogenous compounds were maintained between optimal cultivation levels (NH3–NH4+ = 0.73 ± 0.43 mg/L, N–NO2− = 0.09 ± 0.05 mg/L, N–NO3− = 3.22 ± 0.11 mg/L). Heterotrophic bacteria (6.6 ± 3.4 × 105 CFU/ml) and chlorophyll-α concentration (108.5 ± 80.2 μg/L) showed a similar development pattern, indicating a strong relationship between bacteria and microalgae during cultivation. Vibrio spp. concentrations were low (1.24 ± 1.42 × 103 CFU/ml). It was shown that the photo-heterotrophic system could be used in hypersaline conditions, typical of semi-arid regions, to consistently produce between 12.1 and 14.7 t/ha in 15 weeks.