Outdoor Hatchery Larval Biology and Seed Production of Ganga River Prawn Macrobrachium gangeticum (Bate)

Macrobrachium gangeticum (Bate) the third largest freshwater prawn in habitat in the river Ganga and Brahmaputra, which drain into Bay of Bengal. Seed production of this species (M. gangeticum) in India is done in indoor hatcheries. An outdoor hatchery system has been developed by the author at ICAR Research Complex for Eastern Region, Patna, in which M. gangeticum post larvae are produced. Larval rearing trials for M. gangeticum were carried out during the year 2008. The hatchery shades were covered with non transparent polythene sheets at the roof top to avoid direct sunlight. Larvae were reared in brackish water of 8-14 ppt (part per thousand) salinity for growth and development. Ten thousand larvae were stocked in 300 L tank and fed with live nauplii of Artemia salina twice in a day and after that 1 or 2 days, green algae developed in the larval rearing tank due to open sunlight, these algae were found to be ingested by larvae. The larvae fed voraciously and grew faster because of availability of green algae in the larval rearing tanks. The larvae passed through 15 molts, showing the characteristics of 11 distinct larval stages. First occurrence of post larvae (PL) has been recorded within 20 days and trial was conducted on the 35 days. The water quality parameters viz. water temperature, salinity, pH, dissolved oxygen; total hardness and alkalinity were recorded. Production of PL in trials during rearing was 6,480 and 5,870 with 21.6 and 19.56 PL/L respectively. The result of the present trials, the post larval production and shorter larval duration in M. gangeticum indicated the potential of commercial culture and hatchery operation in inland region.