Sea bass (Dicentrarchus labrax) larvae were fed from day 15 to day 35 with 4 isoenergetic formulated diets that varied in protein (30, 40, 50, 60%) and carbohydrate (37, 27, 17, 7%) content. The diets were designated as P30, P40, P50 and P60, respectively. Best growth and survival were noted for P50 larvae. Poor growth and survival were observed for P30 larvae. The specific activity of amylase increased in direct relation to the dietary carbohydrate level from day 18 onwards. This increase was the result of extensive amylase synthesis. Trypsin activity was positively correlated with dietary protein level only at day 35. This study shows that the mechanisms involved in amylase regulation are efficient in very young sea bass larvae, while those related to trypsin appear later in ontogeny and thus suggests an age-dependent regulation of enzyme synthesis.