Steelhead Trout (Oncorhynchus mykiss)

Steelhead Trout
(Oncorhynchus mykiss)
Photo: NOAA's Monterey Bay
National Marine Sanctuary

Did You Know?

· Steelhead and rainbow trout are the same species.

Status
ESA Endangered - 2 DPS
ESA Threatened - 9 DPSs
ESA Species of Concern - 1 DPS

More information on all 15 steelhead trout DPSs is available on NOAA's National Marine Fisheries Service (NMFS) Northwest Regional Office website.

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

Species Description
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 much more pointed head, 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 two years and females at three. Juvenile steelhead may spend up to seven 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 three 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, stream-maturing or ocean-maturing, 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.

	Steelhead Trout Critical Habitat (click for larger view PDF)
	Steelhead Trout Range Map (click for larger view PDF)

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.

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
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
Salmonid species on the west coast of the United States have experienced dramatic declines in abundance during the past several decades as a result of human-induced and natural factors. For more information, please visit our Pacific salmonids threats page.

Conservation Efforts
A variety of conservation efforts have been undertaken with some of the most common initiatives including captive-rearing in hatcheries, removal and modification of dams that obstruct salmon migration, restoration of degraded habitat, acquisition of key habitat, and improved water quality and instream flow.

The Pacific Coast Salmon Recovery Fund (PCSRF) was established by Congress in 2000 to support the restoration of salmon species. The fund is overseen by NMFS and carried out by state and tribal governments. The 2006 PCSRF report summarizes their work in detail.

No Pacific salmon have been evaluated for IUCN Redlist conservation status.

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

Regulatory Overview
In 1994, NMFS 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, NMFS 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 listed as a Species of Concern on April 15, 2004.

Critical habitat for 10 west coast steelhead DPSs was designated on September 2, 2005.

See Key Documents below for more details.

Key Documents
(All documents are in PDF format.)

Title	Federal Register	Date
Recovery Plan for Upper Columbia River DPS	72 FR 57303	10/09/2007
Species of Concern Fact Sheet: Oregon Coast DPS	69 FR 19975	03/27/2007
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
Other Steelhead Federal Register notices	various	various
Recovery Plans In Progress and Related Documents	n/a	various

More Information