Effects of selective harvesting and claw ablation of all-male freshwater prawn (Macrobrachium rosenbergii ) on water quality, production and economics in polyculture ponds

摘要

The effects of selective harvesting (SH) and claw ablation (CA) of blue-clawed (BC) prawns on an all-male freshwater prawn–finfish polyculture system were compared with control (Co) in quadruplicate. Ponds were stocked with all-male freshwater prawn Macrobrachium rosenbergii, silver carp Hypophthalmichthys molitrix, catla Catla catla and mola Amblypharyngodon mola at 12 000, 2000, 500 and 20 000 ha−1 respectively. Prawns were fed with pelleted feed. Ponds were fertilized regularly with urea, triple super phosphate and cow-dung. SH of BC prawns in treatment SH and CA in treatment CA started on the 60th day during a 137-day culture and continued at 15-day intervals until the final harvest. Water quality parameters and plankton abundance did not vary significantly (P0.05) among the treatments. Treatment SH resulted in a higher (P0.05) net production of freshwater prawn (437 kg ha−1), with better survival and mean weight, followed by CA (354 kg ha−1) and Co (322 kg ha−1). The combined net production of prawn plus finfish was also higher in SH (1244 kg ha−1) as compared with CA (1161 kg ha−1) and Co (1137 kg ha−1), although the finfish production did not differ significantly. The periodic SH of BC prawns showed a better economic return with a BCR of 1.71.