When the spawn is on – A look at the lifecycle of salmon

Salmon are amazing creatures.

There are five species of Pacific salmon native to the freshwaters of Alaska – Chinook (king), Coho (silver), Chum (dog or keta), Sockeye (red) and Pink (humpy). Each species spawns at different times of the year. In this issue of Reel Times we want to take a look at the salmon lifecycle. The salmon lifecycle is a pretty amazing natural occurrence that culminates during the fall months.

As salmon spawn and subsequently die, resident species such as rainbow trout, Dolly Varden and Arctic grayling gorge on eggs and the flesh of decaying salmon. Many fly anglers take advantage of this by using beads (or other patterns that mimic salmon eggs) or flesh fly patterns. Check out our “Fly of the Month” and learn how to tie an effective flesh fly

The Salmon Lifecycle

All Pacific salmon begin their life in freshwater. Female adult salmon dig a redd in the gravel. A redd is an indentation in the substrate where she deposits her eggs. A male and a female will pair up and the female will release her eggs while the male releases his milt. The eggs are fertilized and deposited in the redd. After spawning, the female buries the fertilized eggs in the gravel. The eggs will incubate in total darkness, being covered by gravel, for a certain amount of time.

The eggs hatch in the gravel. The salmon that emerge from the eggs, known at this stage as “alevin,” are not able to swim and will remain in the gravel bed until their mouthparts and fins are fully developed. Alevin are recognized by a yolk sac on the front of their body. The juvenile salmon derives nutrients from the yolk sac as it continues to further develop.

Once the nutrients in the yolk sac have been absorbed and the fish has developed mouthparts and fins, they emerge from the gravel. This stage is called the “fry” stage. Salmon fry are able to swim and begin actively searching for food and shelter. Some species of salmon fry reside in streams and lakes for up to three years (or more), where they eat and continue to grow. Some species, like pink and chum salmon fry out-migrate to the ocean shortly after emerging from the gravel. Juvenile salmon that out-migrate to the ocean are known as smolt.

Salmon smolt continue to feed and grow in the marine environment until they reach the adult stage. At a certain point in a salmon’s adult life, the fish begins making its way back to its natal stream where it will spawn. Salmon will grow in the ocean for 1-5 years before they return to their home streams to spawn. Salmon use various senses like smell to find their way back to the very stream they began their life in.

Age at maturity for salmon varies greatly by species. Pink salmon are 2 years old when they spawn, and some king salmon are up to 8 years old when they spawn. The size of returning salmon directly relates to time spent feeding at sea. Some king salmon can grow to be well over 60 pounds, as they tend to spend more time in the ocean feeding than other, smaller salmon.

Adults that return to their natal stream to spawn are called spawners. Salmon undergo significant physical changes as they prepare to spawn. Each species is different in how they change in appearance. Some develop a deep red or maroon tone to their body, while others, like the chum, develop pronounced calico markings on both sides of the body.

Once the salmon has spawned, the cycle begins again. All adult Pacific salmon die after spawning. The nutrients in their decaying bodies nourish the aquatic ecosystem and provide food for other animals. Even trees along the edge of waterways benefit from the nutrients released through the decay process.