The Unique Lifecycle of Salmon

April 28, 2005

Salmon have a  unique lifecycle. After mature salmon have lived a full long life (up to five years old, depending on the subspecies), they return to the stream or river where they were born in order to spawn. Spawning is how salmon reproduce. Male and female mates swim up their native streambed in search of a good nesting sight. The female creates a nest in the gravel on the bottom of the stream by swishing her tail back and forth to create a safe little area up to 18 inches deep. She prefers a place in a riffle, where the fast-running water will provide an ample supply of oxygen for the eggs. The salmon’s nest is called a redd. The female releases its eggs into the redd, and then the male releases its milt over the eggs. The milt fertilizes the eggs.

After an incubation period, the eggs develop eyes, and then hatch into tiny little creatures called alevin. The alevin have a nutritious egg yolk sac attached to them which nourishes them as they mature. After a period of months, usually in May or June, they lose their egg sacks and emerge from the gravel as fry. The salmon are only about an inch long and are free swimming, making them easy prey for larger fish. They will eat and grow in their native stream for up to a year.

At this point they are called fingerlings and are about 4 inches long. They make their way to the open sea where they will spend up to 5 years growing into adult mature salmon before making their way back to their native stream or river to spawn and die.

And so the cycle begins again…

For an update on the wild salmon fishing season, see the article from CUESA’s 5/1/09 E-letter.