Coho Salmon

A pair of Coho Salmon juveniles, swimming in a shallow stream pool.

The Coho Salmon (Oncorhynchus kisutch) is an anadromous fish, meaning they can adapt and survive in both fresh and saltwater. Coho are one of the more widely recognized species of the pacific salmon group. Their natural range is far reaching, extending to both sides of the Pacific Ocean. This species of salmon has also been introduced into many lakes and reservoirs around the United States, including all four Great Lakes.

Coho Salmon will change color throughout their life cycle, but are commonly called Silver Salmon, due to a silvery coloration on their sides during adulthood in the ocean. However, this color changes when adults head inland to spawn. This amazing process involves the return of these salmon to their home streams, where the fish will often spend time in lagoons or tidelands, using the brackish water to adjust from salty ocean water to incoming fresh water. Once this transformation is complete, the Salmon will then begin their long, arduous journey upstream, using fat stores accumulated in the ocean to swim against the river’s current up to their traditional spawning grounds. This usually occurs when the adult salmon is about three or four years old, and has reached the adulthood, usually weighing in at about eight to twelve pounds. Once the spawning grounds have been reached, females salmon will use their tails to dig nests, or redds, in the stream bed. Male salmon will then fertilize the eggs, then cover them in more gravel to conceal them from predators. The adult Salmon then die, providing food for local animals and fertilizer for plants.

The hidden salmon eggs will incubate for roughly six to seven weeks. When the eggs hatch, the new salmon, called alevin, will typically remain hidden in the gravel, feeding off the egg yolk sac still attached to their bodies. Once the sac is been used up, these fry will then venture out into the stream, feeding plankton and small insects. This behavior will continue until juvenile salmon are strong enough to head downstream to the tidal lagoons, where they undergo their own anadromous transformation and head out to sea to repeat the lifecycle of their parents.

In Muir Woods, Redwood Creek is getting help from the National Park Service and their partner agencies, with the goal of restoring the creek to it’s most natural form in the hope that salmon populations can recover and thrive. Learn more about the Redwood Renewal Project.