Rotifers enriched with a mixed algal diet promote survival, growth and development of barramundi larvae, Lates calcarifer (Bloch)

Fulfilling the nutritional requirements of marine fish larvae, including barramundi (Lates calcarifer), remains a bottleneck for optimal commercial hatchery production. This study investigated the effect of mixed algal diets for the enrichment of rotifers on the survival, growth, development and stress resistance of barramundi larvae. Four groups of 2–13 days-post-hatch (dph) barramundi larvae were fed rotifers enriched with either Nannochloropsis oculata, Chlorella vulgaris, or a blend of 50:50 or 75:25 of N. oculata to C. vulgaris (based on dry weight, DW), respectively. The highly unsaturated fatty acids (HUFAs) docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (ARA) were used as qualitative proxies of the feed. The barramundi larvae fed with the 50:50 diet outperformed all other treatments, with significantly greater larval length (P < 0.05), eye diameter (P < 0.05) and body depth (P < 0.05) at 10 dph, a trend conserved over the whole growth period. The barramundi larvae fed the 50:50 diet also achieved the highest flexion percentage at 10 dph (P < 0.05) and scored the highest survival past the stress test (85%; P < 0.05). The best performing treatment had the second highest level of DHA which suggests that while DHA is an important fatty acid for barramundi larvae it is likely its interaction with other EFA and monounsaturated fatty acid also plays a critical role in their development. Overall, blending microalgae species can enhance the balance of dietary fatty acid for barramundi larvae which in turn can lead to better growth, faster development and higher stress resistance when compared to monospecific microalgal diets