The Life Cycle of Salmon

There are six species of salmon in the Pacific Northwest There are six species of salmon in the Pacific Northwest. The largest salmon, the Chinook, can reach over 6 feet in length and weighs over 100 pounds.

The Salmon Life Cycle In the fall, salmon deposit eggs in the gravel of flowing streams. After spawning (laying eggs), the salmon die sometimes inches from where they were hatched! Amazing instincts! Eggs hatch in the spring, and the alevin grow quickly. Later, the fingerlings continue to grow toward maturity in the streams near their birthplace. As they get closer to their spawning grounds, salmon change in their appearance. Some salmon travel over 1000 miles to lay their eggs. Salmon can grow to be over 100 pounds as they feast in the nutrient- rich waters of the ocean. When full grown, the beautiful, silvery fish begin their migration back to the waters of their birth. When they become strong enough to swim in rushing currents, and quick enough to escape their enemies, the salmon begin migrating to the sea.

Salmon Eggs! As they spawn, salmon may lay up to 12,000 eggs very near the place they themselves were hatched. These are the eyeballs of these tiny salmon!

Alevin Tiny alevin grow quickly after being hatched. When they are as long as your fingernail, they are called fry, and look like real fish! Whey they get to be about as long as your longest finger, they are given a new name -- smolt. As the smolt grow, they eventually begin their migration to the ocean. Smolt Ocean Bound!

These salmon are on their way to the ocean where they may live for 1-5 years, depending on the species, before returning to the rivers and streams to spawn (lay eggs). Only one salmon out of a thousand salmon survives to return to the river to spawn. What are some possible reasons why such a small percentage of salmon actually live long enough to lay eggs?

Along the way are many hazards – some more hungry than others! Going home! These salmon are on their way back to the waters of their birth. Scientists do not know how salmon find the exact location of their birthplace, but their sense of smell (and the chemical signature of the waters) is an important cue. Along the way are many hazards – some more hungry than others!

Replenishing Nutrients When salmon die after spawning, they provide nutrients to plants and animals near the rivers in which they swam. It has been found that 20 % of the nitrogen (an important element for all living things) in evergreen trees that grow next to salmon spawning waters in Alaska actually was carried upstream with salmon. These nutrients are essentially transported from the ocean to the headwaters by the salmon.

Pictures and diagrams found in this photo essay are courtesy of: Credits Pictures and diagrams found in this photo essay are courtesy of: The Alaskan Department of Fish and Game The Washington Department of Fish and Game The Army Corps of Engineers The US National Marine Fisheries