Water Quality, Fish Production and Economics of Nile Tilapia, Oreochromis niloticus, and African Catfish, Clarias gariepinus, Monoculture and Polycultures

Twelve 400 m2 earthen ponds were used to test the effect of Nile tilapia, Oreochromis niloticus, African catfish, Clarius gariepinus, monoculture and polyculture on water quality, fish production and economic performance across a range of stocking ratios: 100% tilapia + 0% catfish, 75% tilapia + 25% catfish, 50% tilapia + 50% catfish, and 0% tilapia +100% catfish. All ponds were stocked at the rate of 3 fish/m2. Two-way ANOVA showed that culture period explained more than 60% of variation in water quality variables while treatment was responsible only for about 11%. Net fish yields were 5.71, 9.84, 11.03, and 11.35 tones/ha corresponding with daily weight gains of 36.60, 63.08, 70.69, and 72.75 kg/ha/d in the 0% catfish, 25% catfish, 50% catfish, and 100% catfish treatments, respectively. Feed consumed was 7.59, 10.84, 13.48, and 17.03 tones/ha for the four treatments, respectively. Fish yield and feed consumption were highest in the catfish monoculture (P < 0.05) followed by the 50% catfish, 25% catfish, and 0% catfish treatments. Net profit for both polyculture treatments was significantly higher than both monoculture treatments, although no significant differences were observed among polyculture or between the two monoculture treatments. The 25% catfish polyculture treatment generated the highest economic returns.