The sockeye salmons swim upstream in the Adams River in the Province of British Columbia, Canada, Oct. 7, 2010. [Xinhua]

As many as 2.5 million sockeye salmons are expected to be flooding into the Adams river this year, which is supposed to be the biggest sockeye run in a century. Sockeye salmons lay eggs in shallower waters of the Adams River in October every year.

After growing for one year in freshwater, the young fish, also known as sockeye fry, migrate downstream to the ocean where they spend the next three years. With near-perfect timing, the instinctive call to spawn draws sockeye adults back to their birthplace with unerring precision. Once reentering freshwater, the fish stop eating and become bright red.

They swim against the river, over rapid torrents during the nearly 500 kilometers journey from the ocean to the Adams River. After getting back home and laying eggs finally, the sockeye are completely exhausted and die.