Abstract
The cod egg contains about 200 nmoles of free amino acids (FAA) at spawning, decreasing to about 100 nmoles at hatching and about 25 nmoles at the end of the yolk-sac stage. The decrease occurs without a corresponding buildup of body proteins but is correlated with ammonia production. The measured oxygen uptake of the developing cod eggs and yolk-sac larvae matches with the oxygen demand necessary to catabolize the FAA lost during this period. The conclusion drawn is that FAA, mainly alanine, leucine, and serine, are the substrate for aerobic energy production of cod eggs and yolk-sac larvae. The implication for the preparation of a favourable first-feed diet of cod larvae, is stressed.