Lifecycle of a Salmon

Adult salmon spend their lives in the open waters of the Pacific Ocean. In the ocean, they feed on zooplankton, crabs, shrimp, and smaller fish like herring or mackerel. Their main predators are orcas, large fish, and seals. After spending between one to seven years in the ocean, salmon will migrate back to their natal streams. When it is time to migrate, salmon will gather in large schools and begin their challenging journey upstream.

Guided by their sense of smell, adult salmon will migrate back to their natal streams to reproduce. As they begin this part of their lifecycle, salmon will transform. Their colour will change, and their jaws will become hooked with sharp teeth. Some species will even develop a hump on their backs! This migration is a lot of work. Salmon travel around 50 km every day, and may leap over obstacles like fallen trees and waterfalls along the way. They won’t even stop to eat because they are so focused on completing this journey!

Salmon that have returned to their natal streams are called spawners. Upon returning, female salmon will use their tails to dig redds, and lay their eggs in them. These eggs will then be fertilized by a male salmon. Most spawners will die after reproduction, which ends the salmon lifecycle. Their bodies will break down and provide nutrients for other living things, such as trees and insect larvae. One spawner can feed thousands of larvae, which then become food for salmon fry!

In the fall, female salmon lay their eggs in gravel nests, called redds, in freshwater streams and creeks. One female salmon can lay thousands of eggs! Male salmon swim over top the eggs and fertilize them. To help protect the eggs, the female salmon will cover them up with gravel. Even though the gravel nests provide some protection, many eggs are eaten by predators, or do not survive the cold winter temperatures.

In the spring, eggs hatch. Newly hatched salmon are called alevins. They are very tiny and helpless, and stay hidden in their redds for protection. Alevins have a yolk sack attached to their bodies, which is their source of food. After 30 to 50 days, the yolk sack will dry up, and alevins will leave their redds to begin the next stage of their life as fry.

No, not a French fry – a salmon fry! Salmon fry continue to grow in the freshwater streams and creeks they were born in (known as their natal streams.) They eat food like insect larvae and fish eggs. Salmon fry have dark stripes along their bodies to help them camouflage. Unfortunately, many salmon fry die from predation, disease, or lack of food. Those that do survive will imprint, or remember, their natal stream’s special scent before beginning their journey to the ocean.

Fry become smolts as they enter the estuary, a place where freshwater from the river meets the salt water of the ocean. The estuary helps salmon smolts get used to saltier water, and prepares them for their journey into the ocean. Eating food like zooplankton and small crabs helps them grow, and gives them energy to avoid predators such as herons and larger fish! Salmon smolts begin to lose their dark stripes and develop silvery scales. This helps them camouflage in the bright, open waters of the ocean.