Born in Alaska’s cold coastal and interior rivers, wild salmon
swim to the open Pacific Ocean to mature and then return to
their native waters to spawn. An anadromous animal, the Pacific
salmon breeds and spends varying portions of its life in fresh
water, then travels to the ocean to feed until maturity. This is
in contrast to palegic species which are born and live solely in
the sea.
As salmon migrate through the cool, pristine waters of Alaska,
they receive nourishment from their natural surroundings. During
their time in the ocean, sockeye, pink and chum salmon feed
primarily on plankton and crustaceans such as tiny shrimp, while
chinook and coho salmon eat smaller fish.
The Salmon Life Cycle
Eggs
Salmon
are born in gravel beds in streams 10 to 700 miles (16 to 1200
km) from the sea. Laid in the fall, the eggs incubate over the
winter, frequently under several feet (more than a metre) of
snow and ice. Their pink eggs are always covered from direct
sunlight. About a month after they have been deposited in the
gravel, eyes begin to show. This normally happens in late
November or early December. It is essential during this time
that water flow and temperature are suitable. The period of
greatest mortality in the salmon's life cycle is in the
egg-to-fry stage.
Hatched Alevins
In
the late winter, the eggs hatch into alevins, tiny creatures
with huge eyes attached to bright orange sacs. They grow rapidly
under the gravel for three to four months. The orange yolk sacs
contain a completely balanced diet of protein, carbohydrates,
vitamins and minerals. The vitelline vein, running through the
centre of the sac, picks up oxygen from the water. The fish at
this stage are totally protected from predators and other
hazards. Good flow of pure water is critically important to
survival of alevins.
New Fry
Alevins
lose their sacs, and emerge from the gravel as fry in May and
June. About an inch (2.5 cm) long, they are free swimming, and
are easy prey for larger fish. In the river, or a nearby lake,
depending on the species, they feed and grow for periods ranging
up to a year or more. (Sockeye fry move into a lake for a year,
although pink and chum fry swim directly to the sea.)
Smolt
In
spring, during the season of freshets, they head downstream to
the sea. They are called fingerlings during this phase of their
lives, and are up to four inches (10 cm) long. In the sea they
spend varying amounts of time ranging up to five years, eating
greedily and growing rapidly in the bountiful ocean feeding
grounds. In the early summer of their maturing year, they
begin to head back to their home streams.
Adult
Salmon
stop feeding as they enter fresh water, living on stored body
fats. They struggle for weeks against rapids, falls,
obstructions in the form of fallen logs and rocks until, bruised
and travel-worn, they reach the placid waters of the spawning
river where they were born. Sockeye and chinooks are the most
hardy of the Pacific salmon family, traveling as far as 1,000
miles (1,600 km) upstream to spawn. Chums, coho and pinks spawn
closer to the sea. With her tail the female digs a nest,
or redd, in the gravel, hollowing out a cavity up to 18 inches
(45 cm) deep. She prefers a place in a riffle, where the
fast-running water will provide an ample supply of oxygen for
the eggs. When the nest is ready, which may be weeks after the spawner has reached the gravel beds, the female lays up to 8,000
eggs in the gravel. The male fertilizes them by covering them
with a milky substance known as milt. After fertilization, the
female covers the eggs with gravel, and remains on the redd
until death several days later. Pacific salmon, unlike Atlantic
salmon, die once spawning is complete.
Salmon
are born in gravel beds in streams 10 to 700 miles (16 to 1200
km) from the sea. Laid in the fall, the eggs incubate over the
winter, frequently under several feet (more than a metre) of
snow and ice. Their pink eggs are always covered from direct
sunlight. About a month after they have been deposited in the
gravel, eyes begin to show. This normally happens in late
November or early December. It is essential during this time
that water flow and temperature are suitable. The period of
greatest mortality in the salmon's life cycle is in the
egg-to-fry stage.
In
the late winter, the eggs hatch into alevins, tiny creatures
with huge eyes attached to bright orange sacs. They grow rapidly
under the gravel for three to four months. The orange yolk sacs
contain a completely balanced diet of protein, carbohydrates,
vitamins and minerals. The vitelline vein, running through the
centre of the sac, picks up oxygen from the water. The fish at
this stage are totally protected from predators and other
hazards. Good flow of pure water is critically important to
survival of alevins.
Alevins
lose their sacs, and emerge from the gravel as fry in May and
June. About an inch (2.5 cm) long, they are free swimming, and
are easy prey for larger fish. In the river, or a nearby lake,
depending on the species, they feed and grow for periods ranging
up to a year or more. (Sockeye fry move into a lake for a year,
although pink and chum fry swim directly to the sea.)
In
spring, during the season of freshets, they head downstream to
the sea. They are called fingerlings during this phase of their
lives, and are up to four inches (10 cm) long. In the sea they
spend varying amounts of time ranging up to five years, eating
greedily and growing rapidly in the bountiful ocean feeding
grounds. In the early summer of their maturing year, they
begin to head back to their home streams. 
Salmon
stop feeding as they enter fresh water, living on stored body
fats. They struggle for weeks against rapids, falls,
obstructions in the form of fallen logs and rocks until, bruised
and travel-worn, they reach the placid waters of the spawning
river where they were born. Sockeye and chinooks are the most
hardy of the Pacific salmon family, traveling as far as 1,000
miles (1,600 km) upstream to spawn. Chums, coho and pinks spawn
closer to the sea. With her tail the female digs a nest,
or redd, in the gravel, hollowing out a cavity up to 18 inches
(45 cm) deep. She prefers a place in a riffle, where the
fast-running water will provide an ample supply of oxygen for
the eggs. When the nest is ready, which may be weeks after the
spawner has reached the gravel beds, the female lays up to 8,000
eggs in the gravel. The male fertilizes them by covering them
with a milky substance known as milt. After fertilization, the
female covers the eggs with gravel, and remains on the redd
until death several days later. Pacific salmon, unlike Atlantic
salmon, die once spawning is complete.