The Incredible Traveling Fish
Salmon is the common name for several species of bony fish of
the family Salmonidae. The family also includes several fish called trout.
Salmon live in the cold freshwater and sea waters in and around the North Pacific
and North Atlantic Oceans. Salmon make one of the most incredible journeys
of all animals. They leave their homes after they hatch and sometimes travel
several thousand kilometers.
Atlantic and Pacific Cousins
There are two groups of salmon. One is the Atlantic salmon. It lives in the
North Atlantic Ocean between North America and Europe. It travels up
rivers that meet the sea on these two continents. Five species of Pacific
salmon live in the North Pacific Ocean. Like the Atlantic salmon,
they live in the ocean and also in the rivers of western North America and
Salmon are anadromous fish. This means they spend part of their lives in freshwater
and part of their lives in the salty ocean. Salmon hatch in streams and
rivers and then swim to the ocean where they eat and grow. They swim
back to the river or stream where they were born to lay eggs.
Salmon get their striking orange-red color from eating tiny orange arthropods
such as krill and shrimp. The coloring can vary from almost white to deep
red. A salmon’s color depends how many and what kind of arthropods
it gobbles up.
The Incredible Journey
The salmon is an anadromous (uh-NAD-droh-muhss) fish. This means that it spawns in
freshwater but spends much of its life at sea. When an Atlantic salmon reaches
the age of two, it leaves its home in the North Atlantic. It begins a migration to
the same place in the river or stream where it was born. It spawns and then
returns to the ocean for two years. After building up its strength, it leaves
the ocean and returns to the rivers to spawn yet again.
For Pacific salmon, the journey may take two to four years. When they reach
their freshwater birthplace, females lay their eggs and males fertilize them.
Unlike Atlantic salmon, the Pacific salmon do not make a return journey to
the ocean. After spawning, Pacific salmon die in the streams, rivers, and lakes
where they were born.
Exactly how salmon find their way is a mystery to scientists. Some experts
think salmons’ sense of smell helps them find and reach their destination.
Others believe salmon have a kind of compass in their brains
that guides them.
Built to Travel
Salmon swim and leap more powerfully than most fish. Their bodies are
also designed to travel long distances.
Click on this strong swimmer to discover more.
The Journey of a Lifetime Begins
A salmon begins as a pea-sized, orange-colored egg laid in the gravel bottom
of a cold freshwater stream or lake. After 50-150 days, the salmon
hatches and swims a little. The egg sac stays attached to the belly like
a little yellow balloon. In the first days, a salmon baby, called alevin
or sac fry, will get all its nutrients from the egg sac. Its
body absorbs the egg sac after a few days. Then, the fry must begin finding
food itself. Small arthropods are the most common food for fry.
Young Salmon: Parr for the Course
Salmon soon develop dark bars on their sides and become much more active predators in
the river. The young fish are called parr during this stage. They will remain
parr for one to three years. This is a dangerous time for them. Parr often
get eaten by birds, other fish, snakes, frogs, and
other predators. But some parr survive. When they reach a size of about 15-20
cm, they start swimming toward the ocean.
To the Ocean!
Smolts are salmon that are old enough and large enough to leave the river and
swim into the ocean. Their bodies go through an amazing change. They
adapt so they can live in the salty water of the ocean. Smolts travel in
large schools for protection but many never make it to the ocean. They get
eaten by larger fish, orca whales, sea birds, bald eagles, and other predators.
Before the salmon returns to its birthplace in two to four years, it will
travel 1,600–5,000 km.
Salmon and People
For centuries, native peoples along the Pacific Coast of North America have
fished for and eaten salmon. Native American legends and ceremonies celebrate
the importance of the salmon to the peoples’ survival and to the whole food
chain. A common Native American legend describes the salmon as a
people. When the Native American people became hungry, they asked the
Salmon People to help them. The chief of the Salmon People finally
People harvest salmon eggs and raise them in fish hatcheries until they are
parr. The parr are then released into the ocean to become adults. Raising
young salmon in a hatchery saves many from becoming food for other animals.
Bears Aren’t the Only Ones Who Like Salmon
Salmon is an important food for people all over the world. Even the eggs are
eaten by some people or used for fish bait by sport fishers. The salmon
industry is worth millions of dollars. Commercial fishing boats in
places like Alaska may catch 50-90% of all the sockeye salmon before they
enter rivers to spawn. Fresh and frozen salmon is shipped all over the world.
Local names people use for different species of salmon include:
- Chinook (also known as the king salmon)
- Chum (also known as dog salmon)
- Pink (also known as humpy salmon)
- Coho (also known as silver salmon)
- Sockeye (also known as the red or blueback salmon)
Salmon Feed Animals
Salmon help many animals survive, too. When the salmon return to freshwater,
they become an important food for bears, bald eagles,
and many other birds and mammals. Even after they spawn and die, the
bodies of the dead salmon become food for many small arthropods living in and
around the freshwater.
Environmental Changes Threaten Salmon
Many salmon die each year trying to make their way up rivers and streams. Trying
to get past dams is often one of the biggest causes of death. Fish ladders,
which are designed to help fish make it safely past dams, have saved large
numbers of salmon since being put into place.
©U.S. Army Corps of Engineers
Throughout most of world, environmental conditions have changed dramatically
over the past 100 years. In Europe and North America, rivers and lakes
where salmon return to spawn have been damaged, drained for irrigation, polluted,
clogged by logging, and blocked by large dams.
Trouble in the Mighty Columbia River
The largest salmon river in the world is the Columbia River in western North
America. The river is 1,954 km long, and salmon have
lived in the river for centuries. Several species of salmon use the
river, but the chinook is the most common. In the late 1800s, over
500,000 chinook were caught each year. In the last 100 years the numbers
have dropped rapidly. In 2005, salmon fishing was put on hold, because
fewer than 2,500 salmon had reached a critical point in the river.
The Forest Factor
Many factors combine to create difficult conditions for salmon. For example,
clear-cut logging of temperate forests leaves hillside soils exposed to wind
and rain. During rainy weather, soil and mud wash into the small streams
and rivers salmon use for spawning. The gravel beds where the salmon
eggs develop become choked with mud and the eggs die. Even though the
cutting of the forest may have happened six months or a year earlier, the impact
can still threaten the survival of the salmon.
Catching too many salmon can be a problem. Overfishing, combined
with environmental damage to salmon rivers, has caused people to become very
concerned about the survival of both Atlantic and Pacific salmon. Most salmon
do not return to the old spawning areas of 50 years ago. Instead, they
are caught. Valuable eggs are removed to be hatched and raised in nurseries
called fish hatcheries. Then salmon are released back into the river after
they become large parr.
The disappearance of salmon is sending a clear signal that more conservation
is needed. Many people and governments now realize that salmon are in crisis.
They are stepping up conservation efforts and passing laws to help restore
and protect salmon and their habitat. In the lower Columbia River Basin,
four Native American groups - the Umatilla, Nez Perce, Warm Springs, and
Yakama – have started Wy-Kan-Ush-Mi Wa-Kish-Wit,or “Spirit
of the Salmon,” a plan that is helping salmon populations in the Columbia