Effects of interaction between nitrite and different salinities on some blood, immunity, and stress indices in juveniles of stellate (Acipenser stellatus)

This study aimed to investigate the effects of interaction between nitrite and different salinities on blood, immunity, and stress parameters in juveniles of stellate (Acipenser stellatus) in two stages. In the first stage, the lethal concentration (LC50 96h) of nitrite in different salinities (0, 4, 8, and 12g/L) to juveniles of stellate was determined. In the second stage, 240 juveniles of stellate (with a mean weight and length of 15.23±2.17g and 17±1.96cm) were exposed to half (50%) of LC50 96h (37.56, 46.77, 120.80, and 176.579mg/L) under the same salinities for 4 days (8 treatments, triplicate). The results showed that the highest mean of white blood cells and neutrophils was in Treatment 7, the highest mean of red blood cells, hemoglobin, MCV and hematocrit was related to treatment 5 and the highest mean of eosinophil belonged to Treatment 8 (P<0.05). Moreover, the highest IgM and total immunoglobulin, lysozyme, cortisol and glucose, and lactate was found in treatments 8, 7, 4, and 3, respectively (P<0.05). The increased nitrite concentration in subjects exposed to salinity plus half of the LC50 96h of nitrite significantly increased the tolerance and immunity parameters and reduced the stress level of subjects. This indicates that salinity could reduce the toxicity of nitrite to subjects. Blood indices also considerably changed in subjects exposed to the same conditions. It can be hence concluded that saline or brackish water (mixed with freshwater, 0 to 12g/L) plus half of the LC50 96h of nitrite is suitable for the culture of stellate juveniles.