Effect of dietary protein level on the growth and survival of pre-adult freshwater crayfish Cherax quadricarinatus (von Martens) in monosex culture

Feeding trials with five levels of crude protein (CP) (22%, 27%, 33%, 39%, and 45%) and digestible energy ranging from 14.32 to 15.21 kJ g−1 were carried out to determine optimum dietary protein for the growth and production of pre-adult freshwater crayfish Cherax quadricarinatus. Triplicate groups of males (ω=23.1±0.58 g) and females (ω=21.8±0.33 g) were fed diets for 70 days in monosex culture. Optimal digestible protein (DP) was estimated for males by fitting mean weight gain to a quadratic model (y=27.86+0.839x–0.0216x2, r2=0.945), and a linear model for females (y=32.84–0.0745x, r2=0.959). Optimal male growth occurred with 25.6% CP, equivalent to 19.4% DP. Male crayfish attained significantly higher final weights and absolute growth rate than females fed the 22%, 27%, and 33% CP diets. The results indicated that a 19.4% DP diet, with a P/E ratio of 11.4 mg kJ−1, produces an optimum growth response for pre-adult C. quadricarinatus under experimental conditions.