Investigations on the use of on-farm resources as pond inputs to culture Tilapia rendalli and Oreochromis shiranus on smallholder farms in rural Malawi

Resources available on the majority of smallholder fish farms in the Zomba District of Malawi were tested to increase smallholder aquaculture production currently limited by a lack of inputs. Napier grass ( Pennisetum purpureum) (NG) and maize bran (MB), isonitrogenous combinations (0.7 kg N ha −1 day −1) of napier grass, maize bran, wood ash (WA) and urea (U) were applied daily and some ponds were stirred (S) twice a week with a rake for 126 days (series 1) and 112 days (series 2) in 200-m 2 ponds stocked with monocultures and 1:1 polycultures of Tilapia rendalli and Oreochromis shiranus at 2 m −2 and 1 fish 0.5 m −2, respectively. Extrapolated net fish yields of up to 3013 kg ha −1 year −1 (series 1) and 2249 kg ha −1 year −1 (series 2) were obtained in NG/MB and S/U/MB/NG/WA treatments. Fry and fingerlings contributed 63–76% and 28–93% to net yields in series 1 and 2, respectively. In series 1, specific growth rates (SGRs) and percent weight gains were significantly higher ( P