Potential and Economic Viability of Freshwater Prawn Macrobrachium rosenbergii (de Man, 1879) Polyculture with Indian Major Carps in Northwestern Bangladesh

Abstract

This study was conducted to assess the aquaculture potential of the freshwater prawn Macrobrachium rosenbergii (de Man, 1879) with the Indian major carps (Catla, Catla catla; Rui, Labeo rohita and Mrigal, Cirrhinus mrigala) and silver carp, Hypophthalmichthys molitrix in northwestern Bangladesh. Further, the effect of the culture system on overall production and economic feasibility was evaluated. A 3×2 (treatment×replicate) experimental setup was conducted using six earthen ponds measuring 100 m² each for a culture period of six months from September, 2007 to February, 2008. The treatments were as follows: T₁ was stocked with only carps (catla, rohu, mrigal and silver) at the 3000 (catla), 2000 (ruhu), 3000 (mrigal) and 2000 (silver) ha^-1; T₂ and T₃ were stocked with catla and silver carp were 3000 and 2000 ha^-1, respectively; and additionally M. rosenbergii (juvenile) was stocked at 15000 and 20000 ha^-1 in T₂ and T₃, respectively. All the ponds were subjected to the same fertilization treatment. Fish were fed twice per day at a rate of 5-12% of the prawn and fish body weight. The net weight gain of catla and silver carp were 69.08±11.63 and 108.67±15.00 g in T_1, 61.76±12.58 and 98.80±17.05 g in T_2, while 58.11±12.51 and 93.09±14.84 g in T_3, respectively. The mean individual weight of harvested prawn was significantly higher in T₂ (14.61±02.06 g) than T₃ (14.04±01.83 g) (P<0.05). Also the survival rate of prawn was higher in T₂ (74.15%) than T₃ (69.25%) (P<0.05). The net production of prawn was higher in T₃ (1141.28±46.35 kg ha^-1) than T₂ (964.54±25.53 kg ha^-1), but the specific growth rate was significantly higher in T₂ (2.07%) than T₃ (1.99%) (P<0.05). Higher profit was obtained in T₃ (35682.18 Tk ha^-1) than T₁ (8537.53 Tk ha^-1) and T₂ (30801.56 Tk ha^-1); however, cost-benefit ratio (CBR) was significantly higher in T₂ (3.19) where stocking densities of prawn was 15000 ha^-1 than T₁ (2.92) and T₃ (2.47). The results of this experiment indicate that the polyculture of the freshwater prawn with the Indian major and Chinese carp present a more profitable venture which is more economically feasible than the monoculture of the freshwater prawn.

DOI: http://dx.doi.org/10.3126/on.v9i1.5735