Life Cycle Stages of Salmon

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.
Alevins stay close to the redd for a few months.

Fry

Fry swim to the surface of the water, fill up their swim bladders with oxygen, and begin to feed.

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.

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.

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.

www.nps.gov