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Evaluation of the suitability of various dry and moist feeds for rearing larvae of the catfish, Heterobranchus longifilis (Teleostei, Clariidae)
Abstract
The effects of various dry and moist diets on water quality, feeding behaviour, mortality and growth of the African catfish (Heterobranchus longifilis) larvae were investigated in a twelve day feeding trial. Five food types and one reference diet were tested in duplicate: Beef liver (BL), beef brain (BB), beef liver and beef brain (BL & BB), toasted soya bean
meal (SB), SB and tilapia fish meal (FM). The reference diet consisted of decapsulated Artemia cysts (AC). One group of larvae received no food (NF) and was included to determine their survival under starvation. The larvae were fed in excess of their requirements, 6 times during the daytime at 2-hour intervals, from the onset of exogenous feeding,
which occurred 56-62 hours after hatching.Water quality did not undergo any degradations likely to induce fish kills. The final mean length (16.7 mm) and weight (38.5 mg), growth rate (3.06 mg.d-1), specific growth rate (31.4 %.d-1), condition factor (0.83) and survival rate (91.4 %) of fish fed decapsulated Artemia cysts were significantly higher than those of fish fed other diets (P less than 0.05). The dry diets based on soya and fish meal led to significantly lower growth and survival rates in comparison to the moist diets based on beef liver and beef brain.The results also indicated that the moist diet based on the mixture of beef liver and beef brain produced the highest specific growth rate (19.04 %.d-1) and survival (68 %) compared to other dry and moist diets. It was observed that larvae in starving conditions increased in length up to 5 days of age, and 7% survived at the end of the trial.
meal (SB), SB and tilapia fish meal (FM). The reference diet consisted of decapsulated Artemia cysts (AC). One group of larvae received no food (NF) and was included to determine their survival under starvation. The larvae were fed in excess of their requirements, 6 times during the daytime at 2-hour intervals, from the onset of exogenous feeding,
which occurred 56-62 hours after hatching.Water quality did not undergo any degradations likely to induce fish kills. The final mean length (16.7 mm) and weight (38.5 mg), growth rate (3.06 mg.d-1), specific growth rate (31.4 %.d-1), condition factor (0.83) and survival rate (91.4 %) of fish fed decapsulated Artemia cysts were significantly higher than those of fish fed other diets (P less than 0.05). The dry diets based on soya and fish meal led to significantly lower growth and survival rates in comparison to the moist diets based on beef liver and beef brain.The results also indicated that the moist diet based on the mixture of beef liver and beef brain produced the highest specific growth rate (19.04 %.d-1) and survival (68 %) compared to other dry and moist diets. It was observed that larvae in starving conditions increased in length up to 5 days of age, and 7% survived at the end of the trial.
