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

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.