A scaling up experiment on cage-cum-pond culture system of African catfish (Clarias gariepinus) and Nile tilapia (Oreochromis niloticus) with carps, developed by AquaFish CRSP, was conducted using 20 farmers’ earthen ponds (65-370 m2) in Chitwan district of Nepal for 150 days to evaluate the production and profitability of these system. The experiment was conducted in a completely randomized design (CRD) with four treatments replicated five times. The treatments were (1) carps in ponds without cage (control), (2) tilapia at 30 fish/m3in cage and carps in open pond, (3) catfish at 100 fish/m3 in cage and carps in open pond, (4) tilapia and catfish at 30 and 100-fish/m3, respectively, in separate cages and carps in open pond. Carps were stocked at 1 fish/m2 (silver, common, bighead, rohu, mrigal and grass carp at 4:2:1.5:1:1:0.5 ratio) in all the treatments. The cage occupied about three percent of the pond area. Caged tilapia and catfish were fed with locally prepared pellet feeds (29% crude protein), while no feed or fertilizer was added into open water of treatment ponds. The control ponds were fertilized weekly using diammonium phosphate (DAP) and urea at rates of 4 kg N and 2 kg P/ha/d.
The results showed that the combined net yields were significantly higher in tilapia-carps (3.0 t/ha/crop) and tilapia-catfish-carp integration system (3.6 t/ha/crop) than control (1.4 t/ha/crop) (p<0.05). The net yields of carps were not significantly different between control and treatments. The cage-cum-pond system increased productivity by 2-3 times. The mean temperature, dissolved oxygen, pH and transparency were not significantly different among treatments. The benefit-cost ratio was significantly higher in the tilapia-carps integration system (7.4) than control (3.3) (p<0.05). This experiment demonstrated that the cage-cum-pond integration with Nile tilapia in cage and carps in open pond is one of the best technologies to increase production and profitability for small farmers.