Life Stages

Life Stages of a Typical Salmon

*Very young fertilized salmon eggs

*Young alevin salmon

Salmon start out as eggs. While nests will carry typically between 500 and 1200 eggs per site, only about 1/5 will survive. Three months after fertilization the egg will hatch into its next life form, an alevin*. Young alevin will carry around its yolk sac and feed solely on it while staying in the protective cover of the gravel for up to 12 weeks. The young salmon, now called a fry develop a vertical striped pattern on their bodies and swim to the surface to fill their swim bladders with air. Fry will spend around a year in their natal streams, hiding amongst the reeds and riparian habitat, feeding off smaller fish and insects. Both physical and environmental cues cause the young fry  to go through a process called smolting, and will result in a new, salt tolerating fish called a smolt. During the process of smolting, scales will become larger, scale color will turn silvery and the tail will both lengthen and enhance its tailfin "v" depth.

*Young, smolting salmon.

Fry with vertical striped pattern.

As the smolt  makes its way to salt water, it stops and feeds gluttonously at the mouth of the river. The bigger the little salmon can get while he is the top of the food chain at the estuary, the better chances it will have when it enters the ocean. Depending on the species of salmon it will mature for 1 to 7 years at sea before making its return journey back to its natal stream, sometimes through several thousands of miles of open sea. From time of fertilization to adulthood, only roughly 2% of all salmon will live to reach adulthood*.

***Interesting Fact***

Salmon noses are so sensitive that they can detect dissolved substances in parts per 3,000,000,000,000,000,000!
 

Once they re-enter fresh water, salmon stop feeding. The accumulated fat and muscle obtained at sea must last them long enough to get them past many obstacles on their way back home. Rapids, dams, and predators lie in their way before they may spawn. Polluted water ways and otherwise degraded habitat make the spawning journey even more treacherous.The spawning salmon will undergo many physical changes during the spawning phase including: emergence of bright colors, humped backs, hooked jaws and sharp teeth**. The salmon relies on smell and chemical cues to guide them to their natal hatching grounds and the females use their tails to create a nest in the gravel. Males attract a mate and fertilize the eggs. Typically within a week after spawning, they will die and become food for the environment and flood the area with nutrients.

*Spawning salmon

References:
*Department of Ecology. Puget Sound Shorelines -  www.ecy.wa.gov
** U.S. Department of the Interior Bureau of Land Management -  www.blm.gov