Guide to Steelhead Salmon (Oncorhynchus mykiss)

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Steelhead salmon
Adult steelheads can usually be found in rivers during the springtime breeding season. USEPA Environmental-Protection-Agency, Public domain, via Wikimedia Commons

Steelhead salmon are anadromous, predatory fish belonging to the genus Oncorhynchus. This group consists of the Pacific salmon and trout and is home to some of the world’s most commercially and recreationally important fish species. With extensive body sizes and delicious fatty filets, the steelhead salmon is an excellent meal choice for humans and wildlife.

Despite their classification as Pacific salmon, steelheads more closely resemble Atlantic salmon (Salmo salar), which has led to some contention about their taxonomic placement with the Pacific salmon in the genus Oncorhynchus.

As sea-faring juveniles and non-breeding adults, steelheads are silver or grey with speckles adorning their dorsal surface, and their bellies are lightly colored with fewer spots. However, breeding adults migrating from the ocean into freshwater undergo a remarkable physical and physiological change. These adults have deep red bellies and cheeks. Their bodies also take on a dark olive color, and their lower jaws become hooked, making them incapable of eating during their migration. By comparison, landlocked steelheads, also known as rainbow trout, are similar in appearance, although their breeding colors are not as intense as the anadromous form.

Steelheads can be found in the Pacific Ocean throughout the year and in clean, clear rivers that lead to spawning grounds. Although young steelheads are found in rivers during the spring and summer, adults can usually be found here during the springtime breeding season. Additionally, this species has been introduced worldwide as a sport fish. Their excellent filets and surprising fight make for an impressive yet practical catch that can readily provide enough nutritious food for a family.

Oncorhynchus mykiss
Steelhead, rainbow trout, trucha arcoiris, redband trout, steelhead trout
Small fish, insects, aquatic invertebrates, fish eggs. Juveniles may eat zooplankton.
Native to the Pacific Coast of the United States and parts of Russia.
50 – 59°F (10 – 15°C). Juveniles need cooler temperatures to hatch and develop.
6 – 8 years
Up to 47 inches (119 cm)
Least concern

Steelhead Salmon Habitat Facts – Where Do They Live?

Steelhead salmon in water
Steelheads travel to the Pacific Ocean in the first year of their life and migrate upstream to freshwater as mature adults to spawn. Garth Harwood / CC BY 4.0

Steelhead salmon are the anadromous form of the landlocked rainbow trout. This means that young steelhead salmon travel to the Pacific Ocean within the first year of life and migrate upstream into freshwater to spawn as adults. In their native range, juveniles migrate to the ocean in the spring. However, they may spend up to two years in freshwater habitats before traveling to estuaries where they become smolts, the stage of juvenile salmon development prior to the adult. From here, they eventually travel to the ocean and become full-fledged steelhead salmon.

Between 3 and 5 years of age, steelheads mature and migrate back into freshwater. On the other hand, rainbow trout are landlocked and cannot migrate to the ocean. Instead, the rainbow trout migrates to deep water lakes or reservoirs as juveniles and then returns to the same swift streams they were born in to reproduce.

The steelhead’s flexible life history makes them an excellent fish to stock in lakes and rivers. Their native range follows the Pacific Coast and connected rivers, but this species has been introduced throughout the United States and many other countries. The landlocked rainbow trout is the only form that can survive outside of its native range because the anadromous form needs to migrate to the Pacific Ocean. Since they are popular sportfish and can complete their life cycle in their landlocked state, steelhead smolts are introduced to lakes and rivers as sportfish that eventually develop into rainbow trout.

What Do Steelhead Salmon Eat? (Steelhead Salmon Diet Facts)

Zooplankton make up a large part of the steelhead diet, especially for juveniles. Matt Wilson/Jay Clark, NOAA NMFS AFSC., Public domain, via Wikimedia Commons

Just like their lifestyle, the diet of the steelhead salmon is varied, although they are generally predatory. In addition, the steelhead diet varies seasonally and with age.

Steelhead diets consist primarily of zooplankton, true fly larvae, and caddisfly larvae during the spring. Summertime diets are the most varied. In the fall, steelheads consume caddisfly larvae, mayfly larvae, and true fly larvae. Finally, their winter diet consists chiefly of fish and zooplankton.

Presumably, juveniles prioritize smaller prey items like zooplankton and insect larvae, whereas adults target adult insects and small fish. Sea-faring juveniles and adults also have an appetite for squid and large aquatic invertebrates. Small prey species like herring, sardines, and anchovies make up the bulk of the adult steelhead salmon’s diet. Adults also enjoy the eggs of other salmonid species.

When fishing for steelhead salmon, worms, bait fish, and salmon roe are great bait options.

Steelhead Salmon Spawning Facts

Group of steelhead trout
During spawning, males & females pair up, the female digs a nest, and then the pair of fish deposit eggs and milt into the nest together. Oregon State University / CC BY-SA 2.0

Steelhead salmon travel long distances to reproduce, and their parents establish this distance because steelheads return to the same spawning grounds they were born in. In addition to anadromy, steelhead salmon also exhibit natal philopatry, this tendency to return to the place of an organism’s birth to spawn. They can do this using remarkable chemoperception (their sense of taste and smell) and memory. Adult steelhead salmon undergo a physically demanding metamorphosis that facilitates their upstream migration, which can cause significant physiological damage. Their energy reserves are devoted solely to reaching their spawning grounds and reproducing. With this single goal in mind, migrating adults have little need to hunt for food.

When adult steelheads have reached their spawning grounds, males and females pair up, with the male guarding the female against predators and competing suitors. First, females dig nests or “redds” into the substrate using their caudal fin. Then, the two salmon deposit eggs and milt into the redd before moving upstream to dig another. Usually, digging the second redd buries the eggs of the first redd. The pair will do this several times and may deposit between 200 and 8,000 eggs.

Generally, adults that have finished spawning are weakened and die soon after if predators do not pick them off. Many wildlife species like bears, birds, and other fish depend on annual salmon migrations as a reliable food source. Remarkably, steelheads rarely survive their migration and can sometimes reproduce twice. They are the only salmonid known to do so. Their landlocked form does not undergo this phenomenal metamorphosis and can breed for several years. This allows rainbow trout to live twice as long as steelhead salmon.

Once hatched, hatchlings remain within the nest for up to three weeks until they can survive in the open water.

Steelhead Salmon Fishing Considerations 

Juvenile steelhead salmon in hands
Hatcheries can help to reduce the steelhead salmon mortality rate as they protect hatchlings in the first few vulnerable weeks of life. Pacific Southwest Region USFWS from Sacramento, US, Public domain, via Wikimedia Commons

Wild animals are not the only organisms that depend on salmon for food. Salmon hatcheries take advantage of the steelhead salmon’s reliable reproductive habit by seeding hatchery grounds with fertilized salmon eggs and scenting the water. Hatcheries significantly reduce mortality during these critical developmental periods by hatching and protecting hatchlings during their first few weeks of life. This ensures that once the salmon are released into the wild, they return to their hatchery, where they are easily captured and processed.

Hatchery salmon are significant for conservation because they provide a sustainable source of salmon without taking wild fish from their native environment. By farming salmon via hatcheries, suppliers can ensure consistent supplies of salmon to consumers at the supermarket. In addition, hatchery fish are easily identified by anglers because their adipose fins are removed before the fish are released into the wild. States often do not regulate hatchery salmon harvest, whereas wild salmon have strict bag limits and limited seasons.

Due to the salmon’s migratory nature, its harvest must be managed through treaties and cooperation with other governments. The United States has established treaties with foreign countries across the ocean and with native tribes that rely on steelhead salmon as a source of food. In addition, salmon are of incredible cultural importance to native people.

Whole fish and filets are not the only resources produced by steelhead salmon. Their roe is harvested and sold as caviar for a high price. This product is only harvested and sold by specific NW Washington Native Tribes that sustainably harvest adult fish for their flesh and eggs.

Wild steelhead salmon are not of conservation concern globally. However, steelheads are considered endangered in several states by individual states and the Environmental Protection Agency. Threats to steelhead salmon are varied but the destruction of their migration routes due to dam construction and habitat degradation are primary contributors to local population declines.

Keyla P
About the author

Keyla P

I have a bachelor’s degree in Natural Resources focusing on Wildlife Ecology and a minor in Entomology. I am also an award-winning student researcher with five years of experience with wildlife-related research.

Read more about Pond Informer.

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