Strategic manipulation of inland saline groundwater to produce Macrobrachium rosenbergii (De Man) post larvae ATUL KUMAR JAIN*, KOYYA DHANA RAJU, GIRISH KUMAR, PRAVEEN KUMAR OJHA and APPIDI KRISHNA REDDY Central Institute of Fisheries Education, Versona, Mumbai – 400 061, India Abstract A series of four experiments were conducted in inland saline groundwater (ISGW) for successful development of the giant freshwater prawn Macrobrachium rosenbergii (De Man) post larvae (PL). The ISGW of 58 ppt was diluted to 12 ppt with freshwater. The concentrations of calcium, potassium and magnesium in ISGW were compared with those of natural seawater (NSW) of equal salinity; they were 340.6, 30.0 and 144.7 mg l–1 in ISGW and 175.0, 174.4 and 425.0 mg l–1 in NSW, respectively. In the first experiment, newly hatched larvae of M. rosenbergii were reared both in ISGW and NSW of 12 ppt. The larvae survived only up to 11 days in ISGW and developed only up to stage IV, whereas they developed normally to PL in NSW within 40-50 days with 6.33±0.88% survival. In the second experiment, the concentration of calcium in ISGW of 12 ppt was reduced to 168.3 mg l–1. The larvae developed to stage IV, but the survival period increased up to 15 days. In the third experiment, the concentration of potassium in ISGW of 12 ppt was increased separately to 60% (102.2 mg l–1) and 100% (170.5 mg l–1) in addition to reduced calcium (168.3 mg l–1). The larvae became completely metamorphosed to PL with 6.66±0.76% survival at 60% potassium in a period of 39-50 days but not at 100% potassium. In the fourth experiment, the concentrations of calcium, potassium and magnesium in ISGW were kept the same as those in the case of 60% potassium, but larvae were reared in a recirculating system. The survival of PL increased to 34.56±1.87% with a rearing period of 23-45 days. The study suggests that ISGW of 12 ppt that contained 168.3 mg l–1 calcium, 102.2 mg l–1 potassium and 144.7 mg l–1 magnesium could be used for the development of M. rosenbergii PL.   < back .