The effects of stocking density on hemolymph bio-chemical parameters and heat shock proteins as stress indicator in shrimp (Litopenaeus vannamei)

Two separate experiments were conducted in this study. In the 1st experiment; at nursery stage, the effects of high stocking densities (200, 400 and 800 pcs per m2) on shrimp (Litopenaeus vannamei) growth, feed consumption, gene expression levels of heat shock proteins (HSP) in different tissues (HSP70 and HSP90) and stress tolerance (formalin, salinity) were investigated. The results showed that shrimp post-larvae reached 1.35, 1.09 and 1.12 grams with 77%, 78% and 82% survival rates, respectively. Salinity and formalin stress tests have shown that high stocking leads to susceptibility in shrimp. HSP70 and HSP90 levels increased with the increase in stocking density, but were regulated to normal levels within 1-2 days. At grow-out stage, in order to determine whether different stocking densities (40, 80 and 160 pcs per m2) create stress in shrimps; growth, feed consumption, some hemolymph and immunological parameters and heat shock proteins were investigated in the 2nd experiment. At the end of the four month trial, it was determined that survival rate of the shrimp ranged from 62.0% to 77.50% and weights between 18.31 and 22.15 g. It was observed that high stocking densities affected serum total protein and triglyceride levels at 2 months, but this effect disappeared at 4 months. Immunological parameters did not show any significant difference at 2 or 4 months. In the hemolymph samples taken at 2 months, phagocytic and lysozyme activities did not differ. HSP70 and HSP90 findings revealed that biomass level of 2 kg/m2 (4.74 kg/m3) caused chronic stress in shrimps.