Feed costs are one of the most prohibitive challenges to production of tilapia in Sub-Saharan Africa., making them unaffordable for the rural poor. This project aimed to reduce production costs of tilapia by reducing the reliance on formulated feed, by partial substitution with live black soldier fly (BSF) larvae produced locally BSF production was set up in a polytunnel in Rukungiri, Uganda. Flies bred freely and eggs were collected and incubated in maize flour where they were left until 2 days post hatch. At this point, the young larvae were inoculated into fruit and vegetable waste, collected from a local market. All waste was mashed using a hammer mill, mixed and stored in drums until time of use. Concrete bays of 1m2, 40cm depth and a 30° slope situated in a covered shed were used to grow larvae for 20 days. A feed trial was conducted on tilapia in fertilised ponds to assess the feasibility of partially substituting feed for BSF larvae. Larvae were substituted for feed at 33% and 66% on a live wet weight basis and tested against a commercial feed only diet and fertilisation only treatment. 100 acclimated tilapia of 42g were randomly stocked in hapas within a fertilised pond in three replicates of each treatment. Fish were fed at 3.5% body weight per day split equally between 3 rations during the day (apart from the fertilisation only treatment). Total weight of fish were taken on a weekly basis to calculate feeding rates for each individual hapa and individual weights were taken every three weeks. Fish were harvested after 15 weeks. Total feed, weight gain, Specific Growth Rates and Feed Conversion Ratios were recorded for each replicate. Economic data was collected on labour effort and costs to set up and manage BSF larvae production, the cost of feed and the income from fish, larvae and associated frass production.
Results showed that there was no difference in the growth rate or survival between all the fed treatments but the treatment that received no feed had reduced growth overall and lost weight in the initial period of the trial. The economic data showed that there was a marked decrease in costs required to produce fish supplemented with BSF larvae and that this was a promising method to produce affordable fish for food insecure rural poor in Uganda.