Effects of different carbon sources on water quality, growth performance and survival of western white shrimp (Litopenaeus vannamei Boone, 1931) in zero-water exchange system
Effect of different dietary carbon sources on water quality, growth performance and survival of western white shrimp Litopenaeus vannamei post larvae was investigated in zero-water exchange system. Shrimp postlarvae with mean weight of 98.47±8.60 mg and mean length of 22.39± 1.70 mm were fed for 32 days in fiberglass containers with 130 liters volume of water and density of 1 individual per liter in five treatments including one control with water exchange and four biofloc treatments with adding different carbon sources including molasses, starch, wheat flour and mixture of them at equal weight ratios with 15% to 9% of body weight. In the values of water quality parameters including temperature, salinity, dissolved oxygen and pH, no significant differences were observed among the biofloc treatments (P>0.05). Maximum pH (8.27 ± 0.09) and maximum dissolved oxygen (6.37 ± 0.56 mg/lit) was in water exchange treatment. Maximum and minimum level of ammonia was 0.43± 0.34 and 0.09± 0.07 mg/lit in water exchange treatment without floc and biofloc treatment with adding starch of carbon sources, respectively and showed significant difference between treatments (P <0.05). The highest increase in body weight (1640.43± 231.28 mg), growth rate (51.26± 7.23 mg per day), specific growth rate (8.97± 0.42 %/day) and biomass (190.29± 26.83mg) was observed in biofloc treatment with adding molasses and the highest survival rate (90± 0.77%) was obtained in biofloc treatment with adding mixture of carbon sources. The highest feed conversion ratio (1.52±0.23) and the lowest feed efficiency (66.81±7.95) were obtained in water exchange treatment without floc, showing significant difference compared to the other treatments (P <0.05). The results showed that using biofloc technology with zero- water exchange system and adding carbonaceous organic matter could help to recycle waste and improve the water quality. Moreover, the presence of biofloc improved growth performance, feed utilization and production of western white shrimp in zero water exchange rearing system
