Prior to being stocked in the experimental tanks, twelve-day-old L. vannamei postlarvae (PL; a mean weight of 3.0±2.0 mg) were acclimated in a raceway (3.6×0.8×0.7 m) with a density of 5 PL per liter; the initial salinity was 35 g L 12−1
,andoveraperiod of 6 days, freshwater was continuously added until the salinity in the raceway reached 0.6 g L−1
. Postlarvae were maintained under these last conditions 6 days for observation and increased their growth (habituation period). . During the acclimation period, the shrimp were fed with a 50% crude protein dry diet (Zeigler 400–600 μm) that was supplemented with newly hatched Artemia nauplii (100 nauplii postlarvae−1 day −1). The diet was fed five times daily (at 7:00, 10:00, 14:00, 16:00 and 19:00 h) . The survival of the acclimatization and habituation period was of 90%. Once acclimated shrimp postlarvae (initial weight 82±10 mg) were stocked into the experimental tanks at a density of 50 PL m−2 in groundwater with a salinity of 0.6 g L−1.