Duplicate groups of 60 European seabass (mean weight 2.1 g) were fed for 9 weeks with 7 isonitrogenous (46% crude protein, CP) and isolipidic (12% ether extract) semipurified diets obtained by adding graded levels of L-arginine to a basal diet. By analysis of dose-weight gain relationship, the dietary arginine requirement was found to be 3.9 g/100 g CP (N'6.25). A similar value (3.8 g/100 g CP) was obtained when the 5 h (peak) post-prandial plasma urea response relative to that of fish fea the basal diet were regressed against the dietary arginine level, suggesting the possible use of this parameter to validate the arginine requirement estimated from growth data.
