World Aquaculture December 2020

WWW.WA S.ORG • WORLD AQUACULTURE • DECEMBER 2020 69 ( C O N T I N U E D O N P A G E 7 0 ) The final daily growth (DG) was not different between polyculture (0.37 g/day) and monoculture (0.35 g/day). Growth was lower during the fall, corresponding to lower temperatures. For summer season, growth was greater but also not different between polyculture (0.58 g/d) and monoculture (0.51 g/day). During fall (March to May) average DGwas 0.26 ± 0.08 g/day (0.20 g/day for polyculture and 0.32 g/day for monoculture), with no statistically significant differences among seasons. No statistical differences were found for growth among monoculture and polyculture either March- April or April-May. Table 2 shows detailed daily growth of each pond month by month. After 113 days, the final mean weight of red claw in ponds fed with only alfalfa hay at a rate of 500 kg/ha/mo was 49 g (Metts et al. (2007). The same study reported significant greater final weight (68 g) of crayfish fed a diet containing 13 percent protein and receiving alfalfa hay. Thompson et al . (2004) reported final weights between 70 g and 80 g with initial weights of 4.6 g in 117 days. The results obtained by Metts et al . (2007) with only alfalfa hay are comparable to those reported in this work. Some experiences show greater growth with the use of foods with a higher protein content. Metts et al . (2009) observed greater growth with diets containing 32 percent protein while Thompson et al. (2004) did not find growth differences among diets with 22, 32 and 42 percent protein content. The use of diets for fish with different protein levels produces variation in the growth of red claw crayfish needs to be evaluated. Tilapia Growth Initial weight of tilapia for polyculture ponds was 28 ± 7 g and 29 ± 8 g respectively. After 117 days, the final weight was 218 ± 39 g and 241 ± 36 g, daily growth (DG) varied among 1.6 and 1.8 g/d (average 1.7 g/d). Table 3 presents a summary of the data obtained in both systems. Daily growth of tilapia was 1.7 g/day, with an average final weight of 229 g after 117 days. In previous assays done at CENADAC, Martin et al. (2007) found final weight of 243 g (Iw = 42 g) with daily growth of 1.5 g/day after 133 culture days in small- volume cages. Tidwell et al . (2000) showed final weights 119 g and 149 g (Iw = 26 g) after 84 culture days of polyculture of tilapia and freshwater giant prawn. A longer culture period and starting culture with bigger fingerlings size to achieve market size should be evaluated. Survival Crayfish survival was 92 percent for polyculture (89-95 percent) and 94 percent for monoculture (82-100 percent), with a final crop density of 1.38 and 1.40 crayfish/m 2 respectively. Survival was satisfactory and greater than those reported by Thompson et al . (2004; 46-61 percent) and Metts et al . (2009; 60-70 percent), both with a crayfish density of 2.5/m 2 . Naranjo et al . (2004) showed a density-dependent survival decrease from 84 percent at 5 crayfish/ m 2 to 63 percent at 20 crayfish/m 2 , relating to possible negative interactions (territorial behavior) that could have great influence over TABLE 2. Daily growth ( g /day). POLYCULTURE MONOCULTURE DATE Pond A Pond B Pond C Pond D Pond E Jan-Feb (22 days) 0.71 0.58 0.31 0.21 0.41 Feb-Mar (27 days) 0.43 0.60 0.46 0.79 0.86 Mar-Apr (29 days) 0.27 0.34 0.78 0.40 0.32 Apr-May (39 days) 0.06 0.14 0.12 0.14 0.17 TABLE 3. Summary for each type of culture. POLYCULTURE MONOCULTURE Crayf ish Tilapia Crayf ish Initial mean weight (g) 1.5 29 1.2 Final mean weight (g) 42 229 47 Initial density (ind/m 2 ) 1.50 0.82 1.50 Final density (ind/m 2 ) 1.38 0.67 1.40 Production (kg/ha) 585 1537 665 Mortality (%) 7.8 18.1 6.4 Initial biomass - Bi (g) 625 5748 538 Final biomass - Bf (g) 17,544 46,120 19,950 Bf-Bi (g) 16,919 40,372 19,412 Days fed 80 50 Feed supplied (kg) 57.2 28.6 FCR 1.42 1.49 Daily growth (g/d) 0.35 1.72 0.39