Effects of Salinity and Ca2+: Mg2+ Ratio on Nutrient Profile, Physiological Responses and Clinical Signs of Penaeus vannamei (Boone, 1931) Reared in Inland Saline Ground Water

Background: A 60-day experiment was conducted to evaluate the combined effect of salinity and Ca2+: Mg2+ ratio on the nutrient profile, physiological responses, and clinical signs of Penaeus vannamei reared in inland saline ground water. Methods: The study used three different salinities viz. T1 (5 ppt), T2 (10 ppt) and T3 (15 ppt) with four different levels of Ca2+: Mg2+ ratios such as 1:1, 1:2, 1:3, and 1:4. A total of 720 healthy post larvae of P. vannamei (mean body weight of 3.70±0.02 g) were stocked (20 shrimp/tank) in 36 circular plastic tanks (100 L capacity each). Each treatment was triplicated following the 3 × 4 factorial design. Result: A significant increase of protein and ash contents and decrease of moisture content were noticed with increasing salinity. The study found no significant difference in the carbohydrate and crude lipid content of P. vannamei. A linear relationship between salinity and serum osmolality was observed which indicated significant increase of osmoregulatory capacity with increasing salinity. The treatment groups fortified with deficient level of Ca2+: Mg2+ ratio showed prominent changes such as abdominal white muscle on dorsal side and muscle cramps. Based on the results, it can be concluded that the better physiological adoption of P. vannamei was observed in 10 and 15 ppt salinities of ISGW fortified with Ca2+: Mg2+ ratio 1:3.