Effects of Stocking Density of All-male Macrobrachium rosenbergii (De Man, 1879) in Polyculture Ponds on Production and Economics

A study was conducted to evaluate the effects of stocking density of all-male freshwater prawn Macrobrachium rosenbergii (De Man, 1879) on water quality, production and economic return in polyculture ponds. Trials involving three stocking densities of all-male prawn viz., 15,000, 20,000 and 25,000 ha^-1 were carried out in replicates, combined in polyculture with fixed densities of silver carp, catla and small fish mola at 1,500, 1,000 and 20,000 ha^-1, respectively. Commercial prawn feed and fertilisers were applied routinely to all ponds. Blue-clawed males were harvested periodically at 15-day intervals over a 5-month culture cycle before final harvest. Differences in prawn density (treatments) did not significantly (P 0.05) affect any water quality parameters. Mean weight of prawn at harvest decreased significantly (P 0.05) with increasing stocking density. Net production of prawns however, was significantly higher at prawn densities of 25,000 and 20,000 ha-1 (661 kg. and 640 kg.ha^-1, respectively) compared with 15,000 ha^- 1(535 kg.ha^-1). Silver carp and catla production did not differ significantly among density treatments, while production of mola was higher at 20,000 prawn.ha^-1. This treatment also resulted in higher net production of all species combined (1,688 kg.ha^-1) as well as the highest return (US$ 2,597 ha^-1).