Salmon: A Keystone Species

Pacific Salmon are more than just fish—they are a keystone species, the lifeblood of this coast, and an enduring icon of the Pacific Northwest. Their epic migration, spanning thousands of kilometers from the Pacific Ocean to the very mountain streams where they were born, fuels entire ecosystems. As they return to spawn, salmon deliver a flood of nutrients that sustains an incredible diversity of wildlife, from towering forests to the smallest microorganisms. Their journey is a testament to resilience, connecting land, water, and communities in ways that have shaped this region for millennia. Protecting salmon means protecting the health of our rivers, forests, and all who depend on them.

 

The Lifecycle of Pacific Salmon and Their Role in the Ecosystem

The lifecycle of Pacific salmon is a remarkable journey of survival, transformation, and renewal. These fish go through several distinct stages, each playing a critical role in their development and the ecosystems they inhabit.

Pacific salmon begin their lives as eggs buried in the gravel beds of freshwater streams and rivers. These eggs are highly vulnerable, requiring clean, oxygen-rich water to develop. After several weeks or months, depending on the species and water temperature, they hatch into tiny fish called alevins. Alevins remain hidden in the gravel, surviving on the nutrients stored in their yolk sacs. During this stage, they are extremely delicate and rely on their protected environment to grow strong enough for the next stage of their journey. Once their yolk sacs are depleted, the young salmon emerge as fry and begin actively feeding. Depending on the species, they may stay in freshwater for weeks to years, feeding on small insects and plankton as they grow and develop. Some species, like Chinook and Coho, spend extended periods in streams and lakes, while others, like Pink and Chum salmon, quickly make their way downstream to estuaries.

As salmon prepare for life in the ocean, they undergo a physiological transformation called smoltification. This process allows them to adapt from freshwater to saltwater. Smolts gradually migrate to estuaries, where they adjust to their new environment before heading into the open ocean.In the ocean, Pacific salmon spend one to seven years feeding and growing. They travel vast distances, accumulating energy reserves for their return journey. During this stage, they are a crucial food source for marine predators like orcas, sea lions, and seabirds.

When they reach maturity, salmon embark on their final migration back to their birthplace, navigating rivers and streams with astonishing precision. After an exhausting journey, they spawn and die, completing their life cycle. Their bodies decompose, releasing vital nutrients into the water and surrounding forests.

Chinook Salmon (Oncorhynchus tshawytscha) – “King Salmon”

Identification:

  • Size: Largest of the Pacific salmon, sometimes exceeding 100 lbs.
  • Color: Dark greenish-blue back with silvery sides and a white belly.
  • Spots: Large black spots on the back, dorsal fin, and both lobes of the tail.
  • Mouth: Black gums (“blackmouth”).
  • Spawning Phase: Turns maroon to olive-brown with a hooked jaw in males.

Coho Salmon (Oncorhynchus kisutch) – “Silver Salmon”

Identification:

  • Size: Medium-sized (8–12 lbs on average).
  • Color: Metallic blue-green back, silver sides, and a white belly.
  • Spots: Small black spots on the back and upper lobe of the tail.
  • Mouth: White gums with a black tongue.
  • Spawning Phase: Males develop a pronounced hooked jaw (kype) and turn deep red with dark backs.

Sockeye Salmon (Oncorhynchus nerka) – “Red Salmon”

Identification:

  • Size: Smaller, typically 4–15 lbs.
  • Color: Blue-silver body in the ocean, no distinct spots.
  • Spawning Phase: Turns bright red with a green head—one of the most striking transformations. Males develop a humped back and hooked jaw.
  • Unique Feature: Unlike other salmon, Sockeye primarily feed on plankton and have large, glassy eyes.

Chum Salmon (Oncorhynchus keta) – “Dog Salmon”

Identification:

  • Size: Medium-sized (8–15 lbs).
  • Color: Metallic greenish-blue in the ocean, no distinct spots.
  • Spawning Phase: Develops dark vertical bars (red, green, or purple) and large canine-like teeth (hence the name “Dog Salmon”).
  • Tail: No spots, unlike other salmon.

Pink Salmon (Oncorhynchus gorbuscha) – “Humpy Salmon”

Identification:

  • Size: Smallest species (3–5 lbs).
  • Color: Bright silver with a blue-green back and large oval black spots on the back and entire tail.
  • Spawning Phase: Males develop a large hump on their backs and turn brown with dark blotches.
  • Mouth: White gums with a black tongue, similar to Coho.
  • Distinctive Feature: Every odd-numbered year has a significantly larger Pink salmon run

A Vital Nutrient Source for Ecosystems

When adult salmon return from the ocean to spawn and die, their bodies release a flood of marine-derived nutrients into freshwater systems. These nutrients, rich in nitrogen, phosphorus, and carbon, fuel the growth of aquatic plants, algae, and microorganisms. This, in turn, supports insects, juvenile fish, and other small aquatic creatures that form the base of the food web. Even young salmon benefit from the nutrients left behind by the previous generation.

Beyond the water, salmon nourish the land itself. Studies have shown that trees and plants near salmon-bearing rivers grow faster and stronger due to the nutrients salmon provide. In this way, salmon contribute to the health of entire forests, reinforcing the deep connection between land and water.

Wildlife That Depend on Pacific Salmon

Salmon are a crucial food source for over 137 species of wildlife, making them a cornerstone of biodiversity. Some of the most well-known salmon-dependent species include:

  • Bears – Grizzly and black bears rely on salmon as a primary food source, especially in the fall when they need to build fat reserves for hibernation. They often drag salmon carcasses into the forest, further distributing nutrients into the ecosystem.
  • Bald Eagles and Other Birds – Bald eagles, ospreys, herons, and gulls feast on salmon, particularly during spawning season. Eagles can be seen gathering in large numbers along rivers when salmon runs are at their peak.
  • Wolves – Coastal wolf populations have been observed relying heavily on salmon, sometimes even more than on traditional prey like deer.
  • Orcas and Marine Mammals – Resident orcas, particularly the endangered Southern Resident Killer Whales, depend almost entirely on Chinook salmon for survival. Sea lions, seals, and other marine mammals also feed on salmon in coastal waters.

By sustaining so many species, Pacific salmon play a vital role in maintaining healthy and diverse ecosystems. Their survival ensures the continued balance of forests, rivers, and oceans, making their conservation essential for the entire Pacific Northwest.

Pacific salmon are vital to the health of the Alouette Watershed, supporting biodiversity, Indigenous cultural traditions, and local ecosystems. As a keystone species, they provide food for wildlife, cycle nutrients into freshwater and forest environments, and sustain recreational and economic activities. However, salmon populations, including sockeye, face severe threats from habitat loss, climate change, and barriers like the BC Hydro Dam, which blocks their natural migration routes.

We advocate for the restoration of sockeye salmon passage above the dam to reconnect these fish with their historical spawning grounds, ensuring their long-term survival. Community members can support this effort by raising awareness, engaging with policymakers, and participating in conservation initiatives. By working together, we can restore salmon populations and protect the health of the Alouette Watershed for generations to come.

References: