Importance of Docosahexaenoic Acid in Marine Larval Fish

Marine finfish require n‐3 HUFA such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as essential fatty acids (EFA) for their normal growth. But it remained unclear as to which of the n‐3 HUFA, either EPA or DHA, was important. Unlike the freshwater species, the EFA efficiency of EPA and DHA may vary in marine fish. The developing eggs rapidly utilize DHA either for energy or for production of physiologically important substances like prostaglandin. This report reveals that in marine larval fish DHA is superior to EPA as EFA. In the case of red seabream, feeding rotifers incorporating EPA and DHA or an n‐3 HUFA mixture prevented many of the ill‐effects observed when the rotifers were low in n‐3 HUFA. Apart from the best growth and survival in an activity test for the larvae fed on DHA‐rotifer, the incidence of hydrops seemed to be totally prevented dietetically by DHA. Similar results were obtained in larval yellowtail, striped jack, striped knifejaw and flounder. There seems to exist a functional difference between EPA and DHA.