Growth performance of three fishes as compared between monoculture and polyculture rearing systems under high-altitude conditions in Rwanda

A 240-day experiment was conducted to compare the growth performance of common carp, Nile tilapia, and African catfish reared in monoculture and polyculture conditions at the Rwasave Fish Farming and Research Station, Rwanda. Fish juveniles of 67.00±1.90, 50.00±2.10 and 10.00±1.10 g respectively for common carp, Nile tilapia, and African catfish were randomly distributed and stocked at 400 fish per pond of 200 m2. Seven experimental variants were undertaken as follows: T1, carp monoculture: T2, tilapia monoculture: T3, catfish monoculture: T4, carp-tilapia polyculture: T5, carp-catfish polyculture: T6, tilapia-catfish polyculture: T7, carp-tilapia-catfish polyculture. The total weight gain (TWG), daily weight gain (DWG), relative growth rate (RGR), specific growth rate (SGR), coefficient of condition (Km) was calculated during the experimental period. Data were subjected to analysis of variance (ANOVA). Globally, treatment groups in the polyculture showed higher TWG, DWG, RGR, SGR but not significantly different (p ≥ 0.05) from the monoculture groups. Nevertheless, T7 had higher TWG, DWG, RGR, SGR followed by T6 and T4. The African catfish followed by the common carp demonstrated a better growth performance than the Nile tilapia in T1, T3, T4, T6, T7. SGR and RGR for the African catfish in monoculture and polyculture groups were significantly different (p ≤ 0.05) from the common carp and the Nile tilapia. The African catfish and the common carp suit to low temperature conditions of high altitude of Rwanda. The polyculture of carp-tilapia-catfish, tilapia-catfish and carp-tilapia can be recommended in the Rwandan aquaculture industry.