Effects of feeding practical diets containing various protein levels on growth, survival, body composition, and processing traits of Australian red claw crayfish (Cherax quadricarinatus) and on pond water quality

A 117-day feeding trial was conducted in ponds with juvenile Australian red claw crayfish (Cherax quadricarinatus) to evaluate the effects on growth, survival, body composition, and processing traits when fed diets containing three different protein levels (22%, 32%, and 42%), and the effects of feeding these diets on pond water quality. Juvenile crayfish (mean weight of 4.6+/-2.2 g) were randomly stocked into nine 0.02-ha ponds at a rate of 500 per pond (25 000 ha(-1)), and each diet was fed to three ponds. There were two feedings per day, each consisting of one-half of the total daily ration. At harvest, there were no significant differences (P>0.05) in the individual weight, percentage weight gain, or specific growth rate among treatments, which averaged 75.3 g, 1535%, and 2.38% day(-1) respectively. Red claw fed the 42% crude protein diet had significantly higher (P<0.05) feed conversion ratio (7.34) compared with crayfish fed diets containing 22% (5.18) or 32% (5.13) crude protein, and had significantly lower percentage survival (46.1%) compared with red claw fed diets with 22% (61.1%) or 32% (58.2%) protein. Total yield was significantly lower (P<0.05) in red claw fed the 42% protein diet (640 kg ha(-1)) compared with red claw fed diets containing 22% (920 kg ha(-1)) or 32% (904 kg ha(-1)) protein. Mean total ammonia nitrogen (TAN) levels were significantly higher (P<0.05) in ponds with red claw fed the 42% protein diet (0.55 mg L-1) compared with ponds with red claw fed diets containing 22% (0.32 mg L-1) or 32% (0.38 mg L-1) protein. Mean total nitrite concentrations in ponds with red claw fed the 42% protein diet was significantly higher (0.05 mg L-1) compared with red claw fed diets containing 22% (0.01 mg L-1) or 32% (0.02 mg L-1) protein. These results indicate that a practical diet containing 22% (as fed basis) protein may be adequate for pond production of red claw when stocked at the density used in this study, and that a diet containing 42% protein adversely affected levels of TAN and nitrite, possibly reducing overall survival of red claw. Use of a diet with 22% protein may allow red claw producers to reduce diet costs and thereby increase profits.