N-3 HUFA REQUIREMENT OF LARVAL GILTHEAD SEABREAM SPARUS-AURATA WHEN USING HIGH-LEVELS OF EICOSAPENTAENOIC ACID

A feeding experiment on n-3 highly unsaturated fatty acids (n-3 HUFA) requirement in gilthead seabream, Sparus aurata, larvae was carried out using rotifers containing different percentages of n-3 HUFA, ranging from 0.16% to 7.42% on a dry weight basis (DWB). The enriched rotifers showed a direct relationship between their n-3 HUFA contents and the n-3 HUFA concentration in the emulsified lipids. The n-3 HUFA level in fish increased gradually to the elevation of the n-3 HUFA percentage in rotifers. The larvae fed on rotifers containing a low percentage of n-3 HUFA showed poor growth and high mortality. Larval growth, survival and activity were effectively improved by the elevation of the n-3 HUFA levels in rotifers to 5.53% DWB. When the level of these fatty acids in rotifers reached the amount of 7.42%, larval growth, survival and activity were negatively affected. In this treatment the larval eicosapentaenoic acid (EPA) assimilation rate was higher than that found for the docosahexaenoic acid (DHA). These results suggest that, in our experimental conditions, the n-3 HUFA requirement for larval gilthead seabream is about 5.5% in DWB of rotifers.