Salmon of the Pacific Northwest


The salmon spends its entire life on a round trip from its birthplace in a cool clean mountain stream or river down to the ocean, and back upstream again. Fish that make this type of journey to the ocean, where they spend most of their adult lives, are called anadromous fish.

Salmon hatch from eggs that are deposited (or"spawned") in mountain streams, often hundreds of miles from the ocean. Salmon eggs incubate for 1-3 months in gravel spawning beds washed over by cold, clean, oxygen-rich water.

After hatching, the young salmon (called "alevina") remain in the stream gravel for another 1-5 months. During this period they feed on the remainder of their egg sacs.

In late spring or early summer the juvenile fish ("fry") emerge and move into quiet pools, where shading vegetation provides cool water and shelter from predatory fish, birds, and land animals. Juvenile fish hang out in the river until they are about a year old, at which time they begin their migration to the sea.

The trip to the ocean is very dangerous for the young salmon. There are many predators along the way, and there are many natural and human-made hazards. Young salmon (called "smolts") tend to swim their way downstream at night, and hide during the day.


The young salmon instinctively follow the same creeks and rivers used by their ancestors as they make their way during spring runoff to the ocean. As they travel, they undergo a physiological change. This process, called "smoltification," (really -- that's what it's called!) enables the young salmon to make the transition from fresh water to salt water.

Once they reach the mouth of the stream or river, the fish remain in the salty bay for several months, feeding on tiny shrimp, other crustaceans, and the young of other saltwater fish. They grow rapidly, and eventually move into the open ocean.

Up to 90% of the salmon that hatch
never reach the ocean!

Just how far a salmon travels in the ocean, and the direction it heads, will vary. Many salmon follow the circular flow of ocean currents. Some fish will migrate as far as 2,000 miles from their home stream, while others will remain closer to home.

As it travels the deep blue sea, the salmon dines royally on krill (a type of small shrimp), herring, and anchovies. But the salmon can be on the menu for mammals (such as sea lions, dolphins, and whales) and fish such as tuna and sharks. To help even the odds, the salmon feeds mostly at night, when it is harder to see. The salmon's coloration also provides camouflage -- seen from above, its dark, spotted topside looks a lot like the deep ocean, while from below, its silver belly blends in with the silvery sky above.

After maturing, and spending most if its life in the ocean, the salmon migrates back home to spawn in the same river or stream in which it was hatched. This journey is very difficult, and salmon have to fight their way upstream, over rocks, past waterfalls, and around human-made obstructions such as hydroelectric dams. Salmon are guided on this journey by the smell of their home waters, which they can detect from among all the other smells in the downstream flow.

The hump on a mature salmon's back
helps make it stable in fast-moving water!

While traveling upstream, the salmon doesn't eat, but lives off of stores of fat in its body. Male salmon develop hooked snouts and humps, and their skin changes color from silver to red, green, or black, depending on the species.

The female salmon, upon reaching the creek in which she was hatched, digs a hole in the gravel (called a "redd"). Then, side by side, a female and male salmon discharge their eggs and sperm into the prepared gravel. After they have spawned, the adult salmon die.

A female Pacific Salmon deposits 1,500
to 7,000 eggs in her spawn!


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