Steelhead (Oncorhynchus mykiss)


The steelhead is a rainbow trout that migrates to sea as a juvenile and returns to freshwater as an adult to spawn. Steelhead and strictly freshwater-dwelling rainbow trout share the same scientific name.

There are no major physical differences between the two, although the nature of their differing lifestyles results in subtle differences in shape and general appearance and a greater difference in color.

Other Names

steelhead trout, steelie, sea-run rainbow.

Identification

Steelhead are generally slender and streamlined. Coloration on the back is basically a 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 that blends more toward white on the stomach.

Steelhead have white leading edges on the anal, the pectoral, and the pelvic fins, and spawners develop a distinct pink to red striplike coloration that blends along the side, both above and below the lateral line.

Size/Age

Steelhead are typically caught from 5 to 12 pounds, and fish exceeding 15 pounds are not uncommon in some waters. Most fish returning to rivers are 5 to 6 years old, and they can live for 8 years. The all-tackle world record is a 42-pound, 2-ounce Alaskan fish caught in 1970.

Life history/Behavior

Most populations appear in rivers in the fall, entering freshwater systems as adults from August into the winter. Spawning takes place in the winter and the spring. The ragged and spent spawners move slowly downstream to the sea, and their spawning, rainbow colors of spring return to a bright silvery hue.

Lost fats are restored and adults again visit the feeding regions of their first ocean migration. Generally, juvenile steelhead remain in the parent stream for roughly 3 years before migrating out to saltwater.

Food and feeding habits

Steelhead in the ocean consume squid, crustaceans, and small fish.

Distribution

The original steelhead range in North America extended from Alaska's Kenai Peninsula to the Baja Peninsula in Mexico, and far inland in coastal rivers. Northern California, Oregon, Washington, southern Alaska, and especially British Columbia have had significant steelhead populations.

Overfishing, pollution, dams, other habitat alterations, and additional factors have adversely affected many native runs of steelhead.
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