The present study reports the influence of salinity (5, 15, 25 and 35 g/L) on the biochemical and immune parameters of Fenneropenaeus indicus challenged with 5. 5 × 104 copy number of White Spot Syndrome Virus. F. indicus that were reared in 25 g/L, were injected with WSSV, and then transferred to 5, 15, 25 (control) and 35g/L were examined for total haemocyte count (THC), phenoloxidase (PO) activity, superoxide dismutase (SOD) activity, alkaline phosphatase assay and acid phosphatase assay after 0∼120 h. It was concluded that the F. indicus transferred from 25 g/L to low and higher salinity levels (5 g/L, 15 g/L and 35 g/L) had reduced immune indices and decreased resistance against WSSV infection. After 120 h, the mortality rate in WSSV injected F. indicus experimental groups (5 g/L and 35 g/L) was significantly higher than in F. indicus exposed to 25 g/L and 15 g/L salinities. During the experimental period (0-120 h), biochemical variables viz. total protein, total carbohydrate, and total lipid levels were measured in the hemolymph of both experimental and control groups. Acute salinity changes induced an increase in protein variations across the salinity ranges in shrimps. The THC, and PO activity, decreased significantly while SOD activity, alkaline phosphatase activity, and acid phosphatase activity was increased in the shrimp held at lower salinity of 5 g/L, 15 g/L and 35 g/L after 24 h.
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