Washington Symbols, State Fish: Steelhead Trout

Adopted in 1969.

The steelhead trout is an anadromous fish, meaning it returns to fresh water rivers to spawn. The scales of the steelhead shine flecks of silver with a gray spotted back from head to tail and an intensely white belly; the two colors separated by a hint of opalescent pink. Steelhead trout is one of the most popular fish for recreational fishing, a major industry in Washington State.

The steelhead trout (Oncorhynchus mykiss *) is a rainbow trout that has spent a part of its life in the sea. There are no major physical differences between rainbow and steelhead trout; however, the nature of their differing lifestyles has resulted in subtle differences in color, shape, and general appearance.

*Until 1988, steelhead (the anadromous form of rainbow trout) was classified in the genus Salmo along with Atlantic salmon, brown trout, and several western trout species. With additional osteology and biochemistry data, biologists have now reclassified steelhead as members of the genus Oncorhynchus. The reason for this is that new information suggested that steelhead are more closely related to Pacific salmon than to brown trout and Atlantic salmon. As such, the American Fisheries Society/American Society of Ichthyologists & Herpetologists Committee on Names of Fishes voted unanimously to accept Oncorhynchus as the proper generic name. For full scientific details, see Smith, G. R., and R. F. Stearley. 1989. The classification and scientific names of rainbow and cutthroat trouts. Fisheries 14 (1): 4-10. As such, the scientific name of steelhead was changed from Salmo gairdneri to Oncorhynchus mykiss. The generic names of the golden, Mexican golden, Gila, and Apache trouts were also changed to Oncorhynchus. Since all of these western trouts including steelhead are biologically capable of repeat spawning and do not die after spawning, it has been suggested this group be called the Pacific trout.

Other Common Names:

Coastal Rainbow Trout, Steelies


Identifying Features:

Steelhead trout have a glowing steel-blue body with spots on the upper body. Their tail has radiating rows of black spots.

• Head blunt, jaw short - does not extend past the eye
• Distinct dark spots on dorsal fin
• Square-shaped tail fin with radiating pattern of spots
• Often has reddish stripe along sides, gill cover reddish
• Length up to 45 inches

Description:

Like all trout, the steelhead are positively separated from the various salmon species by having eight to twelve rays in the anal fin. The rainbow trout/steelhead group are then separated from the brook trout, lake trout, and Dolly Varden by the complete absence of teeth at the base of the tongue. Generally speaking, steelhead are more slender and streamlined than resident rainbow. Like rainbow, the coloration on the back is basically blue-green shading to olive with black, regularly spaced spots. The black spots also cover both lobes of the tail. The black coloration fades over the lateral line to a silver white coloration blending more to white on the stomach. Steelhead from the ocean are much more silver than the resident rainbow. On steelhead the typical colors and spots of the trout appear to be coming from beneath a dominant silvery sheen. The silvery sheen gradually fades in fresh water, and steelhead become difficult to differentiate from resident rainbow trout as the spawning period approaches. Steelhead and rainbow lack the red slash on the underjaw characteristic of cutthroat trout, but do have white leading edges on the anal, pectoral, and pelvic fins. Spawning steelhead and rainbow develop a distinct pink to red strip-like coloration that blends along the side, both above and below the lateral line. On steelhead, the rainbow trout coloration gradually fades following spawning to the more characteristic silvery color that the fish display during their ocean journey. The distinct and beautiful coloration of steelhead during the freshwater spawning period is apparently important in regard to the mating and reproductive process. The silvery sheen and streamlined shape of ocean-bright steelhead is essential to survival in the ocean environment.

Juvenile steelhead trout are identical to rainbow trout until the period prior to their ocean migrations. Young trout and stunted adults have eight to thirteen parr marks on their sides. There are five to ten parr marks between the head and dorsal fin. Prior to migrating to the sea, juvenile steelhead become very silvery and resemble miniature adults. They are called smolt during this life phase.

Typical Adult:

Length: Up to 34 inches
Weight: Up to 8 pounds (may reach 24 pounds)
Life span: Up to 11 years

Habitat:

Steelhead trout are anadromous fish, which means they inhabit the Pacific Ocean and Great Lakes area except during spawning season, when they move to rivers and streams. The preferred water temperature is 55-60 °F.

Feeding Behavior:

Steelhead trout feed on immature and adult insects, plankton, crustaceans, fish eggs, and small fish.

Reproductive Behavior (Spawning):

When: Late March through early June
Preferred Water Temperature: 50-60 °F
Where: Steelhead trout spawn in large, swift, boulder-strewn streams at the gravelly tail of pool or riffle at the head of a pool.
How: The female digs several nest-like depressions called "redds" and deposits eggs in each one. The adults do not guard the eggs.