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Steelhead Trout (Oncorhynchus mykiss)

Status | Species Description | Habitat | Distribution | Population Trends | Threats | Conservation Efforts | Regulatory Overview | Taxonomy | Key Documents | More Info

Status

ESA Endangered - 1 DPS
ESA Threatened - 10 DPSs
ESA Species of Concern - 1 DPS

Species Description

Weight:
up to 55 pounds (25 kg), but usually much smaller
Length:
up to 45 inches (120 cm), but usually much smaller
Appearance:
dark-olive in color, shading to silvery-white on the underside with a heavily speckled body with a pink-red stripe along their sides; in the ocean, they become more silver
Lifespan:
up to 11 years;
sexually mature at 2-3 years
Diet:
zooplankton while young;
adults feed on aquatic and terrestrial insects, mollusks, crustaceans, fish eggs, minnows, and other small fishes (including other trout)
Behavior:
migrate from a marine environment into the freshwater streams and rivers of their birth in order to mate;
females will prepare a "redd" (or nest) in a stream area and may deposit eggs in 4-5 "nesting pockets" within a redd

Steelhead trout can reach up to 55 pounds (25 kg) in weight and 45 inches (120 cm) in length, though average size is much smaller.

They are usually dark-olive in color, shading to silvery-white on the underside with a heavily speckled body and a pink to red stripe running along their sides.

They are a unique species; individuals develop differently depending on their environment. While all O. mykiss hatch in gravel-bottomed, fast-flowing, well-oxygenated rivers and streams, some stay in fresh water all their lives. These fish are called rainbow trout. The steelhead that migrate to the ocean develop a slimmer profile, become more silvery in color, and typically grow much larger than the rainbow trout that remain in fresh water.

Adults migrate from a marine environment into the freshwater streams and rivers of their birth in order to mate (called anadromy). Unlike other Pacific salmonids, they can spawn more than one time (called iteroparity). Migrations can be hundreds of miles.

Young animals feed primarily on zooplankton. Adults feed on aquatic and terrestrial insects, mollusks, crustaceans, fish eggs, minnows, and other small fishes (including other trout).

Maximum age is about 11 years. Males mature generally at 2 years and females at 3 years. Juvenile steelhead may spend up to 7 years in freshwater before migrating to estuarine areas as smolts and then into the ocean to feed and mature. They can then remain at sea for up to 3 years before returning to freshwater to spawn. Some populations actually return to freshwater after their first season in the ocean, but do not spawn, and then return to the sea after one winter season in freshwater. Timing of return to the ocean can vary, and even within a stream system there can be different seasonal runs.

Steelhead can be divided into two basic reproductive types, based on the state of sexual maturity at the time of river entry and duration of spawning migration:

The stream-maturing type (summer-run steelhead in the Pacific Northwest and northern California) enters freshwater in a sexually immature condition between May and October and requires several months to mature and spawn.

The ocean-maturing type (winter-run steelhead in the Pacific Northwest and northern California) enters freshwater between November and April, with well-developed gonads, and spawns shortly thereafter. Coastal streams are dominated by winter-run steelhead, whereas inland steelhead of the Columbia River basin are almost exclusively summer-run steelhead.

Adult female steelhead will prepare a redd (or nest) in a stream area with suitable gravel type composition, water depth, and velocity. The adult female may deposit eggs in 4 to 5 "nesting pockets" within a single redd. The eggs hatch in 3 to 4 weeks.

Habitat

Steelhead are capable of surviving in a wide range of temperature conditions. They do best where dissolved oxygen concentration is at least 7 parts per million. In streams, deep low-velocity pools are important wintering habitats. Spawning habitat consists of gravel substrates free of excessive silt.

Critical habitat for 10 west coast steelhead DPSs was designated on September 2, 2005. Critical habitat for the Puget Sound steelhead was designated on February 24, 2016.

Distribution

In the United States, steelhead trout are found along the entire Pacific Coast. Worldwide, steelhead are naturally found in the Western Pacific south through the Kamchatka peninsula. They have been introduced worldwide.

Population Trends

Steelhead Trout
Steelhead Trout
(Oncorhynchus mykiss)
Photo: Ken Hammond, USDA

In recent years, some populations have shown encouraging increases in population size while others have not. Population trends for specific populations can be found in the 2005 status review report for Pacific salmon and steelhead [pdf] [6.3 MB].

Threats

Conservation Efforts

A variety of conservation efforts have been undertaken with some of the most common initiatives including:

The Pacific Coast Salmon Recovery Fund (PCSRF) was established by Congress in 2000 to support the restoration of salmon. We oversee the Fund, and it is carried out by state and tribal governments.

Regulatory Overview

In 1994, we received a petition to list steelhead throughout its range in California, Oregon, Washington, and Idaho under the Endangered Species Act (ESA). On January 5, 2006, we listed nine DPSs of west coast steelhead as threatened and one as endangered. Some of them had been previously listed between 1996 and 1998, but, because of legal and other issues, all listings were reaffirmed and/or revised in 2006.

The Puget Sound DPS was listed as threatened on May 11, 2007.

The Oregon Coast DPS was considered as a Species of Concern on April 15, 2004.

Critical habitat for 10 west coast steelhead DPSs was designated on September 2, 2005. Critical habitat for the Puget Sound steelhead was designated on February 24, 2016.

Taxonomy

Kingdom: Animalia
Phylum: Chordata
Class: Osteichthyes
Order: Salmoniformes
Family: Salmonidae
Genus: Oncorhynchus
Species: mykiss

Key Documents

(All documents are in PDF format.)
Title Federal Register Date
Draft Recovery Plan for Northern California Steelhead, Central California Coast Steelhead, and the California Coastal Chinook   10/2015
Draft Recovery Plan for South Central California Coast Steelhead   09/2012
Recovery Plan for Southern California Steelhead n/a 01/2012
Species of Concern Fact Sheet: Detailed n/a 09/22/2008
n/a 09/22/2008
Recovery Plan for Middle Columbia River DPS   09/30/2009
Recovery Plan for Upper Columbia River DPS 72 FR 57303 10/09/2007
ESA Listing Rule for Endangered and Threatened ESUs 71 FR 834 01/05/2006
Status Review Update of All ESA-Listed ESUs n/a 06/2005
5-year reviews   various
Other Steelhead Federal Register notices various various

More Information

Updated: February 24, 2016