Positive impacts of Nile tilapia and predatory sahar on carp polyculture production and profits

Carp polyculture is commonly practiced throughout south Asia, but traditional aquaculture methods often lead to low fish yields from ponds in this region. Two trials were conducted to evaluate the benefits of adding Nile tilapia and sahar to carp polyculture ponds. The first trial was conducted in 9 earthen ponds for 240 days. This on-station trial stocked ponds with three separate treatments: a) carp only (C); b) carp + tilapia (C + T); and c) carp + tilapia + sahar (C + T + S). Combined net fish yield at harvest was significantly higher in the C + T + S trial (2.58 ± 0.10 t·ha−1·crop−1) compared to the C trial (2.01 ± 0.26 t·ha−1·crop−1). Additionally, gross margin (output value minus input costs) was significantly higher in the C + T + S trial (2357 ± 211 USD/ha) compared to the C trial (1300 ± 316 USD/ha), but not compared to the C + T trial (1569 ± 177 USD/ha). Next, an on-farm trial was conducted in 12 farmer-managed earthen ponds for 165 days. This trial focused on two treatment types: a) C and b) C + T + S. Combined net fish yield at harvest was significantly higher in the C + T + S trial (2.78 ± 0.39 t·ha−1·crop−1) compared to the C trial (2.06 ± 0.14 t·ha−1·crop−1). Gross margin was also significantly higher in the C + T + S trial (3219 ± 367 USD/ha) compared to the C trial (1800 ± 250 USD/ha). The use of these alternative species, along with traditional carp, has the ability to increase fish yield and raise profits in polyculture systems.