Salmon is anadromous fish. Its habits are very strange. Every spring, as soon as the young fish hatch, they enter the sea from Heilongjiang and Wusuli rivers and feed and grow. After three to five years of growth, by the beginning of September, the mature salmon will lay eggs, so it will leave the ocean and enter the rivers, swim upstream, cross the Sea of Okhotsk and swim back to the Wusuli River and Heilongjiang River. They use their special functions to find places where they were born four or five years ago to lay eggs and hatch young fish. Due to the long-distance and arduous back-swimming, long-term lack of food and physical exertion in the breeding process, the parent salmon died shortly after spawning.