Transition from Endogenous to Exogenous Nutritional Sources in Larval Red Sea Bream, Pagrus major

Early growth and morphological development, yolk and oil globule absorption, and initial feeding were studied in laboratory-reared red sea bream, Pagrus major. Based on energy transition and morphological development, the nutritional transition process was divided into four phases as follows: 1) primordial phase (endogenous) : from hatching to ca. 20 hours after hatching (HAH), 2.1-2.9 mm in total length (TL); 2) organogenesis phase (endogenous): to ca. 20-90 HAH, 2.9-3.4 mm TL; 3) early feeding (mixed feeding to exogenous) : to ca. 90-180 HAH, 3.4-4.1 mm TL; 4) intensified feeding (exogenous): beyond 180 HAH, 4.1 mm TL. In comparison with early stage features of other marine fishes, red sea bream larvae have a relatively short mixed-feeding period , which is disadvantageous for survival. However, a high rate of feeding at exhaustion of endogenous nutrition, a reduced time from initial feeding to 100% feeding, and large larval size at the onset of feeding are considered advantageous features for supporting the nutritional requirements of larvae, allowing a smooth transition from endogenous nutrition to exogenous food sources under rearing conditions.