Exploring the nutritional potential of Monoraphidium littorale and enriched copepods as first feeds for rearing Nile tilapia ( Oreochromis niloticus) ) larvae

One of the challenges in the aquaculture industry is providing nutritionally balanced and environmentally sustainable live food for fish larvae. Therefore, the rearing techniques of fish larvae with preferred starter food should be given importance for obtaining optimal hatchery production. Nile tilapia, Oreochromis niloticus larvae just after yolk absorption (body length 0.950 +/- 0.004 mm; body weight 6.00 +/- 0.02 mg) were reared in laboratory conditions for 16 days, feeding with 6 different diets to know their effect on survival and growth. The diets were live Monoraphidium littorale (T-1), live enriched copepods with M. littorale (T-2), powdered M. littorale (T-3), powdered enriched copepods (T-4), live M. littorale + live enriched copepods (T-5), and powdered M. littorale + powdered enriched copepods (T-6). The proximate composition, amino acid profile and fatty acid content of both M. littorale and copepods were analyzed. The biochemical analysis of the dried powder of enriched copepods and M. littorale revealed that both of them are excellent sources of protein, amino acids, and lipids, especially with monounsaturated and polyunsaturated fatty acids. The O. niloticus larvae fed the T-2 diet exhibited the most favourable outcomes, with significantly higher larval gain in weight and percent weight gain, in comparison to the larvae fed other diets (p < 0.001 for all comparisons). The LG% and SGR of the larvae were also significantly higher in T-2 in comparison to the T-1, T-3, T-4, and T-6 (p < 0.001 for all comparisons) except T-5. In addition, the highest percent survival rate of the larvae was observed in T-2 (95 %) followed by T-4 (93 %), T-6 (93 %), T-3 (82 %), T-5 (73 %) and then T-1 (43 %). Based on the present findings, it is recommended that live copepods enriched with M. littorale can be utilized as a starter food for the rearing of Nile tilapia, O. niloticus larvae in hatcheries because of its enriched nutritional profile.