Effect of density on performance and some hemolymph antioxidant parameters of white-leg shrimp (Litopenaeus vannamei) in a biofloc system

The present study was designed to investigate the effect of density on some performance and activity of biochemical parameters of white-leg shrimp (Litopenaeus vannamei). Twenty-day-old larvae (PL30) were distributed at densities of 100, 200, 300 and 400 No. m-2 in twelve polyethylene tanks (working volume of 200 L) containing bioflocks and fed ad libitum using artificial feed. Each triplicate tank was assigned to one treatment. At the end of experiment, performance indicators, antioxidant enzymes activities and some of the stress parameters were determined. The results showed that an increase in the shrimp density under the biofloc system had a significant effect on the growth performance and hemolymph biochemical properties of white-leg shrimp and declined the final weight, daily growth rate and feeding efficiency ratio. However, the amount of biomass increased with increasing density and reached to more than 1.7 folds higher than that in under the density of 100 No. m-2. However, the antioxidant defense parameters including the activity level of superoxide dismutase, catalase and glutathione peroxidase enhanced with increasing the shrimp density in the biofloc system. Cortisol and glucose levels of the hemolymph also showed a decreasing trend with increasing density to 300 No. m-2,