Effect of dietary protein level on growth and survival of juvenile freshwater crayfish Cherax quadricarinatus (Decapoda: Parastacidae)

Protein requirements of juvenile freshwater crayfish Cherax quadricarinatus, with initial mean weight of 1.08 ± 0.34 g, were studied. Juveniles were fed experimental diets containing seven levels of crude protein (CP) (20, 25, 31, 37, 43, 49, and 55%) and 18.73-21.45 kJ g^-1 of gross energy. The highest mean weight and specific growth rate (SGR) (P < 0.05), with values of 9.6 g, and 3.64% day^-1, respectively, were achieved by feeding a diet of 31% CP. This diet resulted in a survival rate of 80% over 60 days of culture at 27°C. The higher protein level tested (55% CP), yielded a significantly (P < 0.05) lower mean weight of 6.4 g. However, there were no significant differences in SGR among the 20, 25, and 49% CP diets. Feed Conversion Ratio (FCR) was close to 1 for all treatments except the lowest (20%) and highest (55%) CP. Optimum protein requirements were estimated by fitting mean weight gain data to a quadratic model (y = 1.142 + 0.484 - 0.0071x², r² = 0.952, P < 0.05). Optimal growth occurred with 34.2% CP, but the results suggest that optimum protein level for 1-g juvenile C. quadricarinatus is 31% in least-cost diets. The information obtained will contribute to the formulation of diets that will enhance production of C. quadricarinatus.