THE IMPROVED INCORPORATION OF POLYUNSATURATED FATTY-ACIDS AND CHANGESIN LIVER STRUCTURE IN LARVAL GILTHEAD SEABREAM FED ON MICRODIETS

Two feeding experiments were conducted to evaluate the suitability of two commercial microdiets as a complementary food for the rearing of l arval gilthead seabream Sparus aurata. The effect of these diets on gr owth, survival and total lipid composition, as well as the histologica l structure of the liver were examined. The results of the first trial highlighted water quality as an important factor for the survival of microdiet-fed larvae. An increase in water flow rate improved larval s urvival despite a reduction in live food supply. An effect of tank des ign on larval growth and survival was observed also and seems to be re lated with the light level inside the tanks; wider light grey tanks ga ve better results than narrower black ones. Microdiet feeding signific antly improved larval growth and increased hepatocyte diameter and pre sence of PAS positive vacuoles suggesting an increased glycogen storag e in comparison with that of larvae fed live prey only. Artificial die ts provided the larvae with a higher amount of lipids and polyunsatura ted fatty acids of the n-3 series, resulting in a higher DHA content i n the total lipid of the larvae fed on microdiets. (C) 1997 The Fisher ies Society of the British Isles.