Growth and Production of Planktivorous Fish Species in Cages Stocked as Monoculture and Polyculture at Khapuadi in Phewa Lake, Nepal

Growth and production of planktivorous fish species were conducted from 6 November 2009 to 6 August 2010 in 15 outdoor experimental cages of 50 m^3 with nylon netting of 25 mm mesh size. These cages were located at Khapaudi, Phewa Lake, Nepal. The growth rate of silver carp (0.32±0.01g.day^-1) in the monoculture system was found to be significantly higher (P 0.05) than that in the polyculture system in different stocking ratios at 7:3, 1:1 and 3:7 of silver carp, Hypophthalmichthys molitrix (Valenciennes, 1844) and bighead carp, Aristichthys nobilis (Richardson, 1845) in cage culture at Khapaudi. But the growth rate of bighead carp (0.48±0.02g.day^-1) in monoculture was found significantly lower than that in the polyculture with silver carp. The extrapolated net production was 1.55 kg.m^-3.yr^-1 and was best at 3:7 stocking ratio of silver carp to bighead carp. The farmers of Phewa Lake can stock fish seed at 3:7 stocking ratio of silver carp to bighead carp to obtain maximum yield per unit area of cage volume.