Effects of thermal stresses on some hematological factors, Stress indexes and histopathologic of gill in Rainbow Trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss) has great importance in terms of meat quality, easy reproduction and sport hunting and is the most important species of salmonides in freshwater. This research was carried out to determine the effect of thermal stresses on some hematological factors and gill tissue in rainbow trout on 300 fish. For this purpose, fishes that have weight of 30 gr selected randomly and were in 5 treatments (Each treatment has three replicates) and these were treatment 1 (control): 14 °C, treatment 2: 28 °C, treatment 3: 25 °C, treatment 4: 20 °C and treatment 5: 5 °C. This action did for 24 hours. The results showed that the highest number of RBC, the highest number of WBC, the highest number of hemoglobin and hematocrit and the lowest levels of glucose and cortisol were in treatment 1 (control), treatment 5, treatment 1 (control) and treatment 1 (control) (P< 0.05). There were no significant differences in other hematological factors (MCV, MCH, MCHC, neutrophils, lymphocytes, monocytes, and eosinophils, respectively (P> 0.05). As well as there were symptoms such as mortality, severe bleeding, chloride cell destruction, hypertrophy or epithelial cell edema, break downing Pilar, break downing epithelial cell, cell necrosis and aneurysm or telangiectasia. In a general conclusion, it can be said that the temperature of 14 °C is more suitable for rainbow trout, because the highest number of red blood cells, hemoglobin, hematocrit, and the lowest levels of cortisol and glucose were observed in the control group.