Red drum larvae were reared from first feeding to 18 days (26 degrees C) post-hatching on semipurified microparticulate diets supplemented with ICES Reference Oils blended to contain varied percentages of n - 3 highly unsaturated fatty acids (HUFA) (2.87, 5.12, 8.89, and 9.61%) and varied ratios of docosahexaenoic acid (DHA) to eicosapentaenoic acid (EPA) (0.66, 1.25, 2.42 and 3.78). Growth was depressed in larvae fed diets with high percentages of n - 3 HUFA (> 5%) but improved as the percentage of n - 3 HUFA was reduced. Growth and survival of larvae fed diets with varied DHA to EPA ratios was unaffected; however, larvae fed a diet with the highest ratio (3.78) exhibited significantly superior performance in a salinity challenge test indicating a possible nutritional requirement for DHA over EPA. (C) 1998 Elsevier Science B.V.