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Man holding a steelhead (Oncorhynchus mykiss) cropped

Steelhead

Anadromous form of the rainbow trout that migrates between ocean and freshwater.

Photo: Tobin John, U.S. Fish and Wildlife Service, Public domain, via Wikimedia Commons

Steelhead are anadromous fish belonging to the species Oncorhynchus mykiss. They migrate from the Pacific Ocean to freshwater rivers to spawn multiple times over a four-to-six-year lifespan.

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  • Steelhead are anadromous rainbow trout that migrate to the ocean.
  • They can live four to six years and spawn multiple times.
  • Adults may reach lengths of 110 cm and weights of 25 kg.
  • Southern California populations are classified as endangered.
  • Homing relies on chemical imprints from natal streams.

What it is

Steelhead represent the ocean-going variant of the rainbow trout. Their bodies feature a silvery sheen with black spots concentrated on the back. A pink stripe runs horizontally along their sides. They possess a rounded head and a powerful tail for navigating strong currents. Adults typically weigh around 3.6 kg but can reach 25 kg. The silver colour distinguishes them from landlocked relatives.

Where it lives

These fish inhabit cold tributaries flowing into the Pacific Ocean across North America and parts of Asia. Populations exist in the United States, Canada, and Mexico. Humans introduced them to the Great Lakes region, where they now thrive in lakes like Erie and Superior. Small numbers also appear in Atlantic Canada waters.

How it lives

Young fish feed on zooplankton before transitioning to larger prey. In the ocean, they consume squid, small fish, and crustaceans. They exhibit strong homing instincts using chemical imprints from their birth streams. This allows them to return to specific spawning grounds after years at sea. Predators include larger marine animals and birds.

Breeding and life cycle

Females dig depressions called redds in river gravel beds. They lay eggs which males then fertilise. The female covers the eggs with sediment for protection. A single female may produce up to 9,000 eggs. Unlike salmon, steelhead survive spawning and may return to the ocean to breed again later.

Steelhead
A drawing made by EveryFish from what this page says. It is a diagram, not a picture of the real fish.

Fish and people

The fish support significant recreational fishing industries in California and the Pacific Northwest. Anglers value them for sport due to their fighting ability. Some populations face threats from overharvest and habitat loss. Conservation efforts aim to restore stream access and improve water quality for sustainable populations.

Status and threats

Many distinct population segments face endangered or threatened status. Dams block migration routes and alter river habitats. Urbanisation and water diversion further reduce available spawning areas. Southern California populations are particularly vulnerable. Recovery programmes invest millions in habitat restoration and fish passage improvements.

Steelhead trout drift in an Oregon stream. (Photo courtesy of Oregon State University)
Steelhead trout drift in an Oregon stream. (Photo courtesy of Oregon State University). Photo: Oregon State University, CC BY-SA 2.0, via Wikimedia Commons
Created by the National Marine Fisheries Service Salmon Recovery Division
Created by the National Marine Fisheries Service Salmon Recovery Division. Photo: D. Crouse, Public domain, via Wikimedia Commons

Questions people ask about Steelhead

What is the scientific name for steelhead?

Steelhead belong to the species Oncorhynchus mykiss. They are specifically the anadromous form of the coastal rainbow trout or Columbia River redband trout. Genetically, they are identical to landlocked rainbow trout.

How do steelhead find their way back to spawn?

Steelhead use chemical imprints from their birth streams to navigate. They detect solute concentrations and chemical profiles. This allows them to identify precise hatching grounds after years in the ocean. They also use the sun and magnetic north for orientation.

Are steelhead different from rainbow trout?

Steelhead and rainbow trout are the same species. The difference is behavioural. Steelhead migrate to the ocean and return to freshwater. Rainbow trout stay in freshwater their entire lives. Steelhead also tend to be larger and less colourful.

Why are steelhead populations declining?

Dams block migration routes and alter river landscapes. Urbanisation leads to water diversion and habitat fragmentation. Overharvest and changing ocean conditions also impact numbers. Southern California populations are especially threatened by these human activities.

Good reading and sources

Where this page comes from

The facts on this page come from the Wikipedia article "Steelhead", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.

It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.

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Photo credits on this page

The small pictures above come from Wikimedia Commons under free licences. Some are cropped to fit.

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