The Salmon Life Cycle
Overview:
The anadromous life history strategy of salmon plays a key role in bringing nutrients from the ocean
back into rivers and the wildlife community. Though it varies among the five species of Pacific
salmon, in its simplest form, it is hatch, migrate, spawn, die. Click on the following numbered steps
to read about the different components of the salmon life cycle:
1, 2, 3, 4, 5, 6, 7, 8
1. Salmon eggs, 2. Alevins, 3. Coho fry, 4. Smolts, 5. The Elwha River draining into the Strait of Juan de Fuca,
6. Coho migrating to spawn, 7. Sockeye spawning, 8. Dead salmon after spawning
Life Cycle Stages:
Alevins in gravel
NPS photo
1 & 2: Eggs & Alevins
The cycle begins in freshwater, when a redd, or a female's nest of eggs, is fertilized. These eggs
remain in the gravel throughout the winter, and the embryos develop. In the spring, the eggs hatch
and alevins emerge. These are tiny fish with the yolk sac of the egg attached to their bellies. Alevins
stay close to the redd for a few months. When they have consumed all of the yolk sac and grown in
size, these fish emerge from the gravel, and are then considered fry.
A coho fry in the Elwha River
Roger Peters - USFWS
3: Fry
Fry swim to the surface of the water, fill up their swim bladders with oxygen, and begin to feed. Depending
on the species, fry can spend up to a year or more in their natal stream. Upon emerging from the gravel, both
pink and chum are already silvery smolts, and head directly to sea. Sockeye fry tend to migrate to a lake,
spending 1-2 years before migrating to sea. Chinook fry usually spend less than 5 months in freshwater, while
coho fry may spend over a year. The survival of fry is dependent upon high-quality stream habitat. Boulders,
logs, shade, and access to side channels is important in allowing fry to hide from predators and prevents
them from getting flushed downstream during flood river-flows.
By the end of their seaward migration, the smolts are silvery all over.
nps photo
4: Seaward Migration
Eventually, environmental cues cause fry to begin their migration downstream towards the oceans. At this
time, smolting begins, and scales grow as they turn a silvery color. At night to avoid predators, small fry (or
developing smolts) allow the river to take them tail-first downstream while larger fry swim actively towards
the ocean. Estuaries, at the mouth of the river, are crucial to the survival of young smolts. While allowing
their bodies to adjust to the new conditions, they feed heavily, hoping to ensure survival in the ocean.
Estuaries provides crucial adjustment habitat for salmon leaving and entering the river.
nps photo
5: Ocean Life
While some salmon remain in coastal water, others migrate northward to feedings grounds. Salmon may
spend one to seven years in the ocean. Certain species have more flexible life history strategies, while others
are more rigid. Coho may spend up to seven years at sea, but typically four. Pink salmon, on the other hand,
spend a fixed 18 months at sea. Sockeye typically spend two years at sea, coho spend about 18 months, and
chinook can spend up to 8 years before journeying back to their natal streams to spawn.
Coho return to spawn in the Sol Duc River.
nps photo
6: Spawning Migration
It is unsure as to how exactly salmon detect their natal streams, though it is suspected that scents and
chemical cues, as well as the sun, play an important role in the homeward migraton. Once the salmon reach
freshwater, they stop feeding. During the course of the journey, their bodies intinctively prepare for
spawning. The taxing journey draws energy from their fat storage, muscles, and organs, except for the
reproductive organs. Males develop hooked noses, or kype, in order to fight for dominance.
A deteriorated salmon dies soon after spawning. Eggs lay unburied in the gravel.
nps photo
7 & 8: Spawning & Death
Upon reaching natal streams, females build nests, or redds. These little depressions in the gravel are
made by the female by turning on her side and using her tail to dislodge stones or pebbles. Males
fight with other males for spawning rights with a female. The dominant male will court the female
and upon spawning, they release eggs and milt simultaneously. The eggs will settle into the gravel,
and the female will cover the eggs with loose gravel and move upstream in order to prepare another
redd. Eventually, both the males and females die, supplying the river habitat with nutrients and the
seeds of the next generation that will someday return to continue the cycle.
Back to main page
http://www.snh.org.uk/salmonintheclassroom/salmon_lifecycle.shtml
good life cycle page
http://www.youtube.com/watch?v=qV30UZ9aF04
you will survive – salmon song and pictures
http://www.youtube.com/watch?v=8x810mszCfU
salmon in toranto
http://www.youtube.com/watch?v=EqmGSexPaEk
salmon life cycle
(Click to Enlarge)
Salmon eggs
Eggs: Adult salmon lay their eggs in special nests in the gravel called redds in late autumn in
freshwater.
The eggs hatch in the spring time (depending on water temperature) into alevins.
Alevins
Alevins: Hatch in spring time whilst still under the gravel. They have yolk sacs which they use
for food whilst buried in the redds.
They emerge from the gravel about four to six weeks after hatching (depending on water
temperature).
Salmon fry
Fry: After the yolk sacs have been used up, the alevins have to start to feed. At this point they
are known as fry. They feed on tiny water organisms and grow quickly during their first year.
Salmon parr
Parr: The salmon are known as parr once they are over a year old. They stay in freshwater for
between one and four years, feeding on small insects and growing larger.
Salmon smolt
Smolts: The parr change into smolts in the spring of their second, third or fourth year. This
change from parr into smolts is the process where the salmon are getting ready to head out to sea.
Smolts head out to sea in shoals during late spring. They are a very distinctive silver colour.
Adult male
Adult salmon: Adult salmon travel great distances at sea to rich feeding grounds in cold
northerly waters and feed on sandeels, krill and herring. The salmon return to the rivers in which
they were born after being at sea for one to four years.
Adult hen
Adult salmon that return to spawn after one year at sea are known as grilse. Adult salmon that
stay more than one year at sea are known as multi-sea winter salmon. Once the salmon start their
journey from their feeding grounds, they do not feed – even when they are back in our rivers.
Kelt
Kelts: After the adult salmon have spawned they are known as kelts. The females have laid all
their eggs and appear particularly thin. The male fish are tired out from fighting with other males
to make sure they spawn with the best females. Some kelts are able to make it back out to sea,
where they will begin to feed and grow strong again. If they are very lucky they may be able to
survive long enough to make it back to their river again to spawn.
Scientists estimate that only around 5% of kelts that make it back to sea, and survive, are able to
make it back to spawn in our rivers!