Stress and hematological responses of beluga sturgeon (Huso huso L.) juveniles held in low or high densities in winter condition after applying anesthesia

This study was performed in order to evaluate the effects of chronic stress (density) and acute stress (handling) existed in culture environments on stress and hematological parameters of beluga sturgeon (Huso huso) under winter condition (below 10°C) after application of anesthesia. Fish with mean (± SE) weight of 399 ± 1.4 g were kept in the low (1 kg/m2) and high densities (8 kg/m2) in three replicates for a week. Then, fish were held under stress condition so that they were quickly removed from the rearing tank and then anesthetized for 2 minutes in container (50 l) includes 400 mg/l clove powder extract. They were then returned to the original tanks. Blood samples were taken before the stress, 1, 3, 6, 12, 24 and 48 hours after application of the stress and stress indicators (cortisol, glucose and lactate) and hematological parameters (hematocrit, hemoglobin, number of red blood cells, MCV, MCH, MCHC, number of white blood cells, lymphocytes, neutrophils, eosinophils and monocytes) were measured. No differences in measured parameters were observed after one week of holding fish at low and high densities. The results of stress indicators, one hour after acute stress and anesthesia showed a significant difference with resting time (P<0.001). Also significant difference was observed on lactate levels between the low density and high density at 3 h after acute stress and anesthesia (P=0.032). Number of white blood cell at 1 and 6 h after acute stress and anesthesia in high density showed significant difference with resting time (P<0.001). MCV showed significant difference between two treatments at 48 h after the stress and anesthesia (P=0.016). The other parameters did not show any significant difference between treatments (P>0.05). The results revealed that beluga has high resistance against chronic and acute stressors and anesthesia. However, it seems that anesthesia could not control the low negative effects of stress even in this condition of low temperature.