The effect of graded concentrations of dietary DHA on growth, survival and tissue fatty acid profile of Senegal sole (Solea senegalensis) larvae during the Artemia feeding period

We examined the effect of dietary docosahexaenoic acid (22:6n-3, DHA) on growth, survival, pigmentation and fatty acid composition of Senegal sole larvae using a dose-response design. From 3 to 35 days post-hatch (dph), larvae were fed live food (rotifers from 3 to 9 dph, Artemia nauplii from 5 to 35 dph) that had been enriched using one of four experimental emulsions containing four graduated concentrations of DHA and constant arachidonic acid (20:4n-6, ARA) and eicosapentaenoic acid (20:5n-3, EPA). Final proportions of DHA in the enriched Artemia nauplii were described as 'nil' (DHA-N, 0.0% total fatty acids, TFA), 'low' (DHA-L, 4.4% TFA), 'medium' (DHA-M, 7.7% TFA) or 'high' (DHA-H, 14.7% TFA). Significant differences among dietary treatments in larval length occurred at 20, 30 and 36 dph, and in dry weight at 20 and 30 dph, although there was no significant relationship between dietary DHA and growth. The stage of eye migration at 20 dph was significantly affected by dietary levels of DHA. No significant differences in survival were obtained. Tissue fatty acid concentrations reflected the corresponding dietary composition. Fish fed DHA-M and -H enriched nauplii tended to accumulate less lipid, mainly oleic acid (OA), in the carcass that might have caused the lower growth in length observed in DHA-H fish. We hypothesise that negligible amounts of dietary DHA required for normal development in Senegal sole larvae relate to a predominance of EPA rather than DHA in the benthic fauna which this flatfish consumes in the wild post-settlement.