OPTIMUM DIETARY-PROTEIN LEVEL FOR GROWTH OF BIGHEAD CARP (ARISTICHTHYS-NOBILIS) FRY IN A STATIC WATER-SYSTEM

Isocaloric diets (290 kcal digestible energy/100 g) with protein levels ranging from 20 to 50% in increments of 5% were fed to bighead carp fry (3.8 +/- 0.2 mg mean body weight and 9.8 +/- 0.1 mm total length) for 7 weeks. Growth in weight and length increased as the protein level of the diet increased from 20 to 30% and decreased as the protein level increased further. Although not significantly different (P > 0.05) from those of fry fed the 25% or 35% protein diet, weight gain (250 mg) and increase in total length (15.7 mm) were highest for fry fed the 30% protein diet. Feed conversion ratio, protein efficiency ratio and survival rate did not clearly indicate the required protein level. The protein requirement was determined using a static-water culture system but assessment of the water quality failed to indicate an association between ammonia concentration and protein in the diet. Further research is necessary to determine why high levels of protein resulted in depressed growth.