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,
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
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
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
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
eggs in her spawn!