38 DECEMBER 2015 • WORLD AQUACULTURE • WWW.WAS.ORG Southern Flounder Grow-out at Blue Ocean Farms Because of problems with the availability of fingerlings, two separate trials were conducted at Blue Ocean Farms. Each trial used two production tanks, one fed diet 1and the other fed diet 2. In trial 1, southern flounder juveniles were stocked into each of two tanks at 650 fish per tank and grown for 10 months. In trial 2, juveniles were stocked into each of two additional tanks at 455 fish per tank and grown for 7 months. Ranges of water quality parameters during trials 1 and 2 were: temperature 22.5-26.0 C, pH 7.4-7.7, salinity 6-20 g/L, dissolved oxygen 5.7-10.7 mg/L, ammonia 0.250.40 mg/L and nitrite 0.05-0.22 mg/L. In trial 1, fish growth was similar between diets, with no differences in mean weight throughout the study (Fig. 6, Table 2). Survival and feed consumption of fish fed the two diets was also similar. The FCR of fish fed diet 2 (1.40) was slightly better than that of fish fed diet 1 (1.82). In trial 2, fish growth, survival and feed consumption was similar between diets (Fig. 7, Table 2). The FCR of fish fed diet 2 (1.40) was slightly lower than that of fish fed diet 1 (1.45). In both trials, a potential cause of low to moderate survival of flounder irrespective of diets was wide fluctuations in salinity of the culture medium which was sourced from a natural estuary where salinity ranged from 6-20 g/L. In both trials, feed consumption and FCRs of southern flounder fed the two diets was similar, suggesting that appetite and growth efficiency of southern flounder were not affected by diet. A diet replacing 30 percent of fishmeal with soybean meal (diet 2) did not reduce growth performance, feed utilization and survival of southern flounder. These results are also consistent with previous laboratory findings that southern flounder juveniles are able to efficiently use diets that replace 35-39 percent of fishmeal with soybean meal for growth (Alam et al. 2011). Diet Effects on Whole Body Proximate Composition A sample of three black sea bass and six southern flounder from each tank were collected at harvest and stored at -20 C for biochemical analysis. Proximate composition of each TABLE 5. Fatty acid analysis (mg/g dry sample) of diets and southern flounder and black sea bass muscle (fillet) at harvest. Values are means of duplicate analysis. Diets Southern flounder fillet Black sea bass fillet Fatty Acid Diet 1 Diet 2 Diet 3 0% 30% 0% 50% 14:0 6.2 5.3 6.7 2.4 2.2 14.6 12.6 16:1n-7 10.8 8.2 11.6 4.5 4.3 28.7 26.8 16:0 19.7 18.7 22.8 12.2 11.1 64.5 64.5 18:4n-3 2.7 1.4 2.5 0.6 0.8 4.7 4.1 18:2n-6 10.8 8.5 14.9 7.3 5.4 28.0 35.5 18:1n-9 18.5 16.3 21.5 12.0 9.8 60.2 67.6 18:0 4.6 4.6 5.0 3.0 2.7 14.7 14.4 20:5n-3 (EPA) 12.4 6.5 11.5 4.2 3.9 22.2 19.8 20:1n-9 1.7 1.3 1.6 1.5 1.3 4.0 3.9 22:6n-3 (DHA) 11.1 5.9 7.9 8.6 7.2 24.1 18.4 22:5n-3 2.6 1.2 2.4 2.8 2.5 6.5 5.7 Σ SFA 30.5 28.6 34.5 17.6 16.0 93.8 91.4 Σ MUFA 31.0 25.7 34.6 17.9 15.3 92.9 98.2 Σ n-3 PUFA 28.9 15.0 24.3 16.2 14.3 57.5 48.0 Σ n-6 PUFA 10.8 8.5 14.9 7.3 5.4 28.0 35.5 n-3/n-6 PUFA 2.8 1.8 1.6 2.2 2.7 2.1 1.4 DHA/EPA 0.91 0.91 0.68 2.05 1.87 1.09 0.93 FIGURE 5. Growth of black sea bass fed a high fishmeal-based diet or a high soybean meal-based diet in 16-m3 recirculating seawater tanks (N = 2 per treatment) for 10 months at Aqua Plantations farm. Each tank was stocked with 1,167 hatchery-reared fish. Plotted points represent means of 150 fish.
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