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

Abstract

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+or-0.01 g.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+or-0.02 g.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.