BackgroundTransfer operations are one of the stress sources that cause mortality in fish. This study investigated the effects of different dissolved oxygen concentrations on oxidative stress and several biochemical parameters during the transfer of adult rainbow trout (Oncorhynchus mykiss). The aim was to determine the optimum dissolved oxygen concentration to minimize stress and potential tissue damage during transfer.ResultThe study analyzed GSH-Px, SOD, and LDH enzyme activities; MDA, Cp, TOS, TAS, OSI, cortisol, glucose, urea, uric acid, creatinine, Ca, Mg, and MDA levels; as well as Cp, TOS, TAS, and OSI values in serum and muscle tissue. Findings indicated that transfer and preparation for transfer induced oxidative damage in fish. Comparing different dissolved oxygen levels, it was observed that hypoxic and hyperoxic conditions increased ROS levels, suppressed the antioxidant mechanism, and caused oxidative stress.ConclusionsAmong the tested conditions, transfer under normoxic conditions with a dissolved oxygen concentration of 10 mg/L was the most effective in minimizing oxidative stress and tissue damage. This suggests that maintaining adequate oxygen levels during transfer plays a crucial role in reducing physiological stress in rainbow trout.