The upriver salmon migration is one of nature's most exciting dramas. But to the five species of Pacific salmon (Chinook , chum, coho, pink, and sockeye), it is a long, strenuous, desperate race against time, with every obstacle taking its toll.
Pacific salmon belong to a group called anadromous fish that includes Atlantic salmon, sturgeon, lampreys, shad, herring, sea- run cutthroat trout, and steelhead trout. These species hatch and live the first part of their lives in fresh water, then migrate to the ocean to spend their adult lives, which may be as short as 6 months or as long as 7 years. When they reach sexual maturity, they return to the freshwater stream of their origin to lay their eggs. Pacific salmon make the round trip only once, but some Atlantic salmon may repeat the cycle several times.
Migration between fresh and salt water occurs during every season of the year, depending on latitude and genetic characteristics of the fish. Groups of fish that migrate together are called runs or stocks. Salmon spawn in virtually all types of freshwater habitat, from intertidal areas to high mountain streams. Pacific salmon may swim hundreds, even thousands, of miles to get back to the stream where they hatched.
However, only a small percentage of salmon live to reach their natal stream or spawning grounds. Those males that survive the trip are often gaunt, with grotesquely humped backs, hooked jaws, and battle-torn fins. The females are swollen with a pound or more of eggs. Both have large white patches of bruised skin on their backs and sides.
Since salmon do not feed once they leave the ocean, some will die on the way because they lack enough stored body fat to make the trip. Many will be caught in fishermen's nets. Those that evade the nets may have t ...