During the yolk-sac stage of the teleosts from the sea, biochemical components such as FAA, protein, FA, total lipid and carbohydrate, vary distinctly and decrease with the development. The decrement varies largely among them. This suggests that in the early development of the fish, its nutrition requirement is not the same. It may change with different species, developmental stage and survival environment. Thus if we know the exact change in the biochemical components, we can find the most appropriate food to meet the larval nutritional requirement and reduce the mortality.