Abstract: To explore the exogenous Sr²⁺ sedimentation on otolith of chum salmon embryos, chum salmon embryos were exposed to culture water contained Sr²⁺ at Sr²⁺concentration of 50, 100, 200 or 400 mg·L^-1 for 48 h to imitate Sr²⁺ sedimentation. After a culturing period of 12 d and 100 d, the otoliths of the chum salmon were taken to detect exogenous Sr²⁺ sedimentation with electroprobe microanalyzer (EPMA). The results showed that obvious deep red strontium signatures were produced in the otolith of chum salmon at different concentrations of Sr^{2 +}. The mean and extreme values of peak strontium area were not stable for the same Sr²⁺ dose, but the lowest of all the peak values was 35.1 times as much as that of control. Overall, the strontium value increased with the increase of Sr²⁺ concentration. The strontium peak had no signs of abating after a culture period of 100 d. The results also showed that strontium was gradually deposited in the otolith, and had obvious hysteresis to immersion. Strontium sedimentation could also return to a normal level after the peak. These characteristics accorded exactly with the requirement of discharge tag technology, which indicated that exogenous Sr²⁺ was suitable in the marking of salmon otolith.