Extensive negative impacts to the seafood industry and marine food webs have occurred due to increased forage fish catch. Forage fish are smaller species of fish (e.g., anchovies and sardines) collected and fed to domesticated fish and shrimp. Forage fish is the main ingredient in fishmeal (FM) and fish oil (FO), and the single highest cost in farming aquatic animals, for fish feed used in the aquaculture industry. Overfishing FM and FO has decreased their availability, inflating costs of fishmeal for commercial fish feeds worldwide. Many seafood farmers in developing countries have also realized that, in the long run, they will be unable to afford FM as a significant protein source in aquafeed (Abdel-Fattah et al., 2020). Incorporating insects as a protein source alongside, or in place of FM or FO, has the potential to increase food security in developing countries and for the aquaculture industry in the future.
A 12-week (84 days) greenhouse feeding trial was conducted with 6 separate recirculating aquaponics systems (RAS) with Nile tilapia (Oreochromis niloticus) and butter lettuce (Lactuca satival). Each system contained 25 fish in 1 m3 fiberglass tanks, a 200 L biofilter, and an 800 L trough with 35 butter lettuce each, supported in floating rafts. Water flowed from the tanks to biofilters, into the floating raft grow beds, and was pumped back to the tanks from the grow beds. Temperature, pH, dissolved oxygen, and conductivity were determined daily for fish tanks. Ammonia, nitrite, and nitrate levels were taken every other day for tanks and biofilters. The objective of the study was to determine the impact of insect meal substitution in fish feed on growth rates of butter lettuce and tilapia. Formulation of the feeds with a 15% and 25% insect meal (IM) substitution included commercial feed, mealworm meal, vegetable oil, and gelatin.
To conclude, plant growth increased with a modified diet of 15% IM treatment and the results were statistically significant (Table 1). The 15% IM treatment also had a higher fish biomass average increase (Table 1).