Salmon

Salmon are fish that live in the cold waters of the northern Pacific and Atlantic Oceans. They are famous for one of the most amazing journeys in the animal world. Salmon are born in freshwater rivers and streams, swim out to the ocean to grow up, and then swim all the way back to the same stream where they hatched to lay their own eggs.

There are several kinds of salmon. The Atlantic salmon lives in rivers and oceans on both sides of the Atlantic. The Pacific group includes chinook, sockeye, coho, pink, and chum salmon. A chinook, the biggest kind, can weigh over 100 pounds. That is about as heavy as a ten-year-old child.

A salmon's life begins in a gravel nest on the bottom of a river. The tiny fish that hatches is called a fry. For a year or two, the young salmon grows in the stream. Then its body changes. Its silver scales get brighter, and its insides shift so it can survive in salt water. When it is ready, it swims downstream to the ocean.

In the ocean, salmon grow fast. They eat smaller fish, squid, and shrimp. A single salmon can travel thousands of miles at sea. Some swim from Alaska almost to Japan before turning back.

After one to seven years, something pulls the salmon home. Scientists think they use Earth's magnetic field like a compass, and then use smell to find the exact stream where they were born. Each river has its own mix of chemicals, and the salmon remembers it like a scent memory.

The journey home is brutal. Salmon stop eating once they enter freshwater. They fight their way upstream, sometimes leaping up waterfalls more than ten feet high. Bears, eagles, and people catch many along the way. The fish that make it change color. Sockeye salmon turn bright red with green heads. Males grow a hooked jaw.

At the end of the trip, females dig nests in the gravel and lay thousands of eggs. Males fertilize them. Then, for almost all Pacific salmon, the adults die within days. Their bodies feed the stream. Scientists have found that trees near salmon rivers grow faster because of nutrients from salmon that died there.

Salmon matter to many ecosystems and cultures. They are central to the food web of the Pacific Northwest, where grizzly bears, orcas, and bald eagles depend on them. Indigenous peoples from California to Alaska have fished for salmon for thousands of years, and still honor the salmon's return each year.