Effect of thermal stress on some hematological parameters of diploid and triploid Rainbow trout (Oncorhynchus mykiss)

Temperature fluctuation is one of the most common stressors during fish transportation and aquaculture condition. Triploid rainbow trout (Oncorhynchus mykiss) get more attention because of its sterility. In this study, 24 rainbow trout belong to diploid and triploid group, average weight 13±0.23 g were subjected to temperature change from 13 to 20 ºC, and kept under tension for 10 min. Before applying the tension and 24 h after, blood samples were taken from 5 individuals from each ploidy groups and some haematological parameters were analysed. Temperature tension caused significant reduction in red blood cell (RBC) counts and haematocrits in both diploid and triploid fish, where the RBC were reduced from 1.25 × 106 cells to 1 and 0.9 × 106 cells in diploid and triploid groups, respectively (P<0.05). On the other hand, the haematocrits levels were reduced up to 25% in both groups after tension applied. While, there were no significant changes observed in white blood cell counts and hemoglobin levels in diploid, the significant changes were visible in triploid ones (P<0.05). The results showed that triploid rainbow trout affected more than diploid ones by thermal stress. Study on some other common stressors on triploid fish were highly recommended.