Screening microalgae strains for fish feed of juvenile Nile tilapia (Oreochromis niloticus) and their zootechnical performance

Fishmeal, the main protein source in fish feed, may become unsustainable due to economic and environmental issues in the fishing industry. In this work, we developed fish feed for juvenile Nile tilapia ( Oreochromis niloticus ) enriched with microalgal biomass as an alternative protein source. Considering the cyanobacterium Arthrospira maxima and the green algae Chlorella sorokiniana and Neochloris oleoabundans , A. maxima biomass was more suitable for the development of fish feed, based on its protein content (~70%), specific growth rate (~0.4 day -1 ), and biomass yield (~2 g L -1 ). Fish feed containing 0, 10, 20, 30, and 40% A. maxima biomass was systematically fed to juvenile Nile tilapia four times a day. The protein and lipid digestibility was above 90% for all experimental diets, higher than generally reported in the literature. After 85 days of feeding, all biometric and growth parameters were significantly improved by the inclusion of A. maxima biomass in the diet ( p < 0.05), except for the apparent feed conversion and protein efficiency ratio. The survival rate, weight gain, and specific growth and development rates increased by 24, 65, 15, and 18%, respectively. The positive effects were more evident during the second half of the experiments and were inhibited by the highest tested A. maxima biomass inclusion (40%). The calculated optimal inclusion level for A. maxima biomass in the juvenile Nile tilapia diet was around 23%. The results strongly support the use of A. maxima biomass as an alternative ingredient and protein source to replace fishmeal in fish feed.