World Aquaculture December 2020

68 DECEMBER 2020 • WORLD AQUACULTURE • WWW.WA S.ORG The remaining population were weighed and counted at the end of the study to determine survival rates and overall yields. Feed conversion ratio (FCR = feed supplied/weight gain) and daily growth rate (DG = final weight–initial weight/time) were calculated. Water quality variables were monitored twice daily, including temperature, dissolved oxygen concentration and pH in the early morning and in the afternoon prior to feeding. Statistical data analyses were performed and treatments groups were subjected to tests of normal distribution by the Shapiro-Wilk test and equal variance homogeneity by the Levene test, and then compared by Student’s t-test using SPSS V21 statistical software. Water Quality Water quality was similar to conditions in a previous study (Wicki et al . 2008). Average water temperature during the culture period was 26 C (Fig. 4), with a maximum of 37.8 C in February and a minimum of 14.7 C in May. Red claw crayfish growth tends to stop at a minimum temperature of 15 C and a mean of 20 C. Red claw growth diminishes with temperatures over 34 C or below 20 C (Jones 1997). The best growth occurred between January and March, when mean water temperature was 28.7 C, and the lowest growth occurred in May when average temperature was 20 C. Mean dissolved oxygen concentration was 7.2 mg/L (Fig. 5). Maximum dissolved oxygen concentration occurred in May with 15.7 mg/L in the afternoon and minimum dissolved oxygen concentration was measured in March with 1.6 mg/L in the early morning. Minimum dissolved oxygen values recorded during the study occurred in the polyculture ponds, with values ranging from 1.6-2.2 mg/L in March and 1.9-3.0 mg/L in May. During the same months, dissolved oxygen concentration in crayfish monoculture ponds were greater than 3.5 mg/L. Red Claw Crayfish Growth After 117 days, average final weights of crayfish were 42 g in monoculture and 47 g in polyculture but were not significantly different. Red claw growth during the culture trial is shown in Figure 6. Wicki et al . (2008) reported an individual harvest weight of 43 g in 91 culture days. FIGURE 3. A 300-m 2 pond with crayfish shelters ready for stocking (CENADAC). FIGURE 4. Water temperature during the production period. FIGURE 5. Dissolved oxygen concentration during the production period. FIGURE 6. Red claw crayfish Cherax quadricarinatus growth during the production period. TABLE 1. Diet formula and composition. Ingredients Feed (%) Fishmeal 20 Meat meal 11 Corn meal 10 Soybean meal 27 Rice bran 30 Minerals and vitamins 2 TOTAL 100 Crude protein (%) 34 Lipids (%) 8 Estimated digestible energy (kcal/kg) 3,360