Evaluation of gradual acclimatization of Litopenaeus vannamei post-larvae to freshwater in tropical regions: Emphasis on biological performance and physiological health responses

Abstract Vannamei shrimp (Litopenaeus vannamei) have long been cultivated in brackish or marine waters in Indonesia. However, production has faced challenges due to outbreaks of Vibrio parahaemolyticus. Research suggests that this pathogen does not thrive at very low salinity levels, prompting interest in low-salinity culture systems. To explore this approach, a study was conducted from March to April 2024 to evaluate the effects of gradual salinity reduction on the survival and physiological health of L. vannamei post-larvae (PL-10). The research was carried out at PT. Mochtar Sani Corporation (MSC), Campang Raya, Bandar Lampung, Indonesia. A Completely Randomized Design (CRD) was employed, consisting of four treatment groups, each replicated three times, namely Control K (Sudden salinity reduction from 10 ppt to 0.5 ppt); Treatment X ( Gradual salinity reduction of 2 ppt every 24 hours); Treatment Y (Gradual salinity reduction of 2 ppt every 48 hours); and Treatment Z (Gradual salinity reduction of 2 ppt every 60 hours).The highest survival rate was recorded in Treatment Y (89.0 ± 4.0%). Statistically, the control group exhibited a significantly lower survival rate (24.0 ± 6.0%) compared to all gradual reduction treatments (P < 0.05), though no significant differences were observed among the three gradual treatments (P > 0.05). Additionally, the specific daily growth rate showed no significant differences among treatments, including the control group (P > 0.05). Physiological health indicators—such as hepatopancreas condition, lipid levels, and intestinal muscle ratio—remained within normal ranges throughout the acclimatization period, indicating that gradual salinity reduction did not negatively impact shrimp health.