free essential amino acids, hematological characteristics, and the immune response in juvenile . Six isonitrogenous and isoenergetic semi-purified diets were formulated to contain graded dietary arginine levels (actual levels: 0.83%, 1.30%, 1.81%, 2.35%, 2.82%, and 3.36%). The protein source consisted of casein-gelatin-fish meal and a crystalline amino acid mixture. The experimental fish (2.6±0.1 g) were randomly assigned among 18 cages (1 m×1 m×1 m, 30 ind/cage). Each experimental diet was fed to fish in triplicate tanks using a completely randomized design. Weight gain rate (WGR) and feed efficiency rate (FER) increased significantly with an initial increase in dietary arginine levels (<0.05), but tended to plateau above a dietary arginine level of 1.81%. The crystalline arginine was used by juvenile , but there was a negative correlation between arginine and lysine content in the plasma. Dietary supplementation with arginine caused a significant increase in urea, total protein (TP) and globulin (GLB) concentrations ( (AST) activity, and an invariable level difference in the plasma glucose (GLU) concentration, alanine aminotransferase (ALT) activity and albumin (ALB) in juvenile relative to the control diet (0.85%). Hemoglobin content (HGB) content, red blood cell (RBC) count, and white blood cell (WBC) count increased significantly (<0.05) with an increase in dietary arginine level between 0.83% and 1.81%. However, there was a significant (<0.05) decrease with an increase in dietary arginine levels between 2.35% and 3.36%. The maximum RBC count, WBC count, and HGB content were observed in animals fed 1.81% dietary arginine. Dietary arginine level significant affected the respiratory burst assay of blood cell (<0.05), and had a negative effect on cumulative mortality in juvenile . Our results suggests that feed supplementation with 1.81% and 2.35% arginine enhances amino acid absorption and stimulates immunity and resistance to pathogenic infection in juvenile