The Life Cycle of Salmon - American Geosciences Institute

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Transcript The Life Cycle of Salmon - American Geosciences Institute

The Life Cycle of Salmon
There are six species of salmon in the Pacific
Northwest. The largest salmon, the Chinook, can
reach over 6 feet in length and weighs over 100
The Salmon
In the fall, salmon deposit
eggs in the gravel of
flowing streams.
Eggs hatch in the
spring, and the
alevin grow quickly.
Later, the
fingerlings continue
to grow toward
maturity in the
streams near their
When they become
strong enough to
swim in rushing
currents, and quick
enough to escape
their enemies, the
salmon begin
migrating to the sea.
Life Cycle
After spawning (laying eggs),
the salmon die sometimes
inches from where they were
hatched! Amazing instincts!
As they get closer to
their spawning grounds,
salmon change in their
appearance. Some salmon
travel over 1000 miles to
lay their eggs.
Salmon can grow to be
over 100 pounds as they
feast in the nutrientrich waters of the
ocean. When full grown,
the beautiful, silvery
fish begin their
migration back to the
waters of their birth.
Salmon Eggs!
As they spawn, salmon may lay up to 12,000 eggs
very near the place they themselves were
These are
the eyeballs
of these tiny
Tiny alevin grow quickly after being hatched.
When they are as long as your fingernail,
they are called fry, and look like real fish!
Whey they get to be about as long as your
longest finger, they are given a new name -smolt. As the smolt grow, they eventually
begin their migration to the ocean.
These salmon are on their way to the ocean where they
may live for 1-5 years, depending on the species, before
returning to the rivers and streams to spawn (lay eggs).
Only one salmon out of a thousand salmon survives to
return to the river to spawn. What are some possible
reasons why such a small percentage of salmon actually live
long enough to lay eggs?
Going home!
These salmon are on their way back to the waters of their
birth. Scientists do not know how salmon find the exact
location of their birthplace, but their sense of smell (and the
chemical signature of the waters) is an important cue.
Along the way are
many hazards –
some more hungry
than others!
Replenishing Nutrients
When salmon die after spawning, they
provide nutrients to plants and
animals near the rivers in which they
swam. It has been found that 20 % of
the nitrogen (an important element
for all living things) in evergreen
trees that grow next to salmon
spawning waters in Alaska actually was
carried upstream with salmon. These
nutrients are essentially transported
from the ocean to the headwaters by
the salmon.
Pictures and diagrams found in this
photo essay are courtesy of:
•The Alaskan Department of Fish and Game
•The Washington Department of Fish and Game
•The Army Corps of Engineers
•The US National Marine Fisheries