Mohammad Hossien khanjani

Effect of different carbon sources on nursery performance of Pacific white shrimp (Litopenaeus vannamei) cultivated in biofloc system was investigated. Shrimp postlarvae (98.47± 8.6mg) were fed for 32 days in tanks with water volume of 130 liter and density of 1 individual per liter. control treatment (clear water) and four biofloc treatments (BFT1, BFT2, BFT3 and BFT4) with adding different carbon sources including molasses, starch, wheat flour and mixture of them, respectively were considered at equal weight ratios. According to the results, salinity, dissolved oxygen and pH were not significantly different among the biofloc treatments (P>0.05). Maximum pH (8.27) and maximum dissolved oxygen (6.35 mg/L) were recorded in the control. Maximum (0.43 mg/L) and minimum (0.09 mg/L) ammonia level were recorded in the control and BFT2, respectively (P<0.05). Using simple carbohydrates (molasses and starch) lowered the ammonia concentration significantly. The highest increase in body weight (1640.43± 231.28 mg), growth rate, specific growth rate (8.97±0.42 %/day) and biomass (190.29± 26.83 mg) were found in BFT1 and the highest survival (90± 0.77%) was found in BFT4. The highest feed conversion ratio (1.52±0.23) and the lowest feed efficiency (66.81±7.95) were observed in the control (P<0.05). The proximate composition analysis revealed an increase in lipid and ash at biofloc treatments. Results indicated that using biofloc technology with zero-water exchange system and adding carbon sources could help to recycle waste and improve the water quality. Moreover, the type of carbonaceous organic matter as a substrate for heterotrophic bacteria is effective in degradation and metabolization of ammonia and nitrite.