Fish samples were placed in uniform areas of the irradiation field to minimize any differences in the geometry of the radiation dose. The samples were treated with 0.25 ± 0.01, 0.5 ± 0.1, 1 ± 0.2, 3 ± 0.03, 5 ± 0.15, 7 ± 0.04, and 9 ± 0.05 kGy in a gamma cell (gamma cell 60Co, dose rate 1.31 kGy/h) at a room temperature of ∼10 °C. Harwell Amber 3042 dosimeters were used to measure the radiation dose. Immediately after irradiation, samples were placed in 2 ml microcentrifuge tubes for DNA extraction. Portions of each sample were also kept in the refrigerator at −20 °C for one and 3 months.