Poor larval nutrition has been identified as the primary cause of the high larval mortality rates in hatcheries of the African bonytongue (Heterotis niloticus). Although, that freshly hatched Artemia nauplii increases survival when given as a starter live feed, the high price of Artemia has prompted research into sustainable substitutes. This study evaluated the effect of different commercial starter feeds on the growth and survival of the African bonytongue, as well as the optimum weaning age of the fry. Four starter diets: decapsulated Artemia, live Artemia, fishmeal, egg yolk, and a combination ratio of 50% boiled egg yolk and 50% wheat flour. Heterotis fry aged 10, 28, and 46 days after hatching (DAH), respectively were fed Artemia nauplii then co-fed with one of the four trial diets for an additional 7 days after which Artemia feeding was completely withdrawn. After this, the fry were maintained solely on the experimental diets for 14 days. A control group was kept on Artemia nauplii throughout the experiment. The results showed that at 10 DAH fish fed the live Artemia had the highest survival rate (97.5 %), decapsulated Artemia had a survival of (7.5%) while all other treatments had no survival. For fry weaned at 28 DAH, survival rates differed significantly (p<0.0001), with Artemia again recording the highest rate (70%), followed by decapsulated Artemia (50%) fish meal (35%), egg yolk and flour (12.5%), and egg yolk (7.5%). At 46 DAH, survival rates similarly varied significantly (p<0.0005), with Artemia at 75%, followed by decapsulated Artemia (60%), egg yolk and flour (27.5%), fish meal (20%), and egg yolk (12.5). The final mean weight, weight gain and survival rate improved significantly (p < 0.05) for fry fed Artemia nauplii compared to the artificial diets. Survival increased significantly (p < 0.05) with weaning age. The lower survival rates (10 - 46DAH) suggest the inability of the fry to digest diet at ages below 46 DAH. Results suggest that live Artemia is the most suitable feed for the larviculture of Heterotis niloticus.
Keywords: African bonytongue, Hatching, Heterotis niloticus, Artemia, and Larval survival