Steelhead Trout (Oncorhynchus mykiss)
Not many anglers know it, but steelhead and rainbow trout are the same
species. The rainbow trout is a species of salmonid native to tributaries of the Pacific
Ocean in Asia and North America. A steelhead is a sea-run rainbow trout
(anadromous) that after two or three years at sea, usually returns to freshwater to
spawn. All steelhead and/or rainbow trout, whichever name you call the Oncorhynchus
mykiss, hatch in a gravel bottom, in a fast-flowing river or stream. Those that stay in
freshwater their entire life are called rainbow trout. Those that migrate to the ocean
grow larger and turn a silver color and are called steelhead.
Steelhead can grow up to 55 pounds and up to 45 inches in length but they average
much smaller in size. They are usually dark-olive in color but change to a silvery-white
on their underside. They have a heavily speckled body with a pink-red stripe along
their sides. When they are in the ocean, they take on more of a silver color.
A steelhead can live up to 11 years. They reach sexual maturity at two or three years.
They feed on aquatic and terrestrial insects, crustaceans, fish eggs, minnows and
various types of baitfish.
Steelhead migrate from their marine environment into the freshwater streams of their
birth in order to mate. They build redds, or nest in the gravel areas of the streams for
Steelhead are a unique species. They develop differently depending on the
environment they are raised in. Most Pacific salmonids can only spawn once.
Steelhead can spawn more than once. These trout can migrate hundreds of miles.
For example, steelhead found in the Clearwater River of Idaho come a long way from
the Pacific Ocean to spawn.
A young steelhead may spend up to seven years in freshwater as a smolt before
migrating to the ocean to feed and mature. They can then remain in the ocean for up
to three years before returning to freshwater to spawn. It should be noted that some
steelhead return to freshwater after their first year in the ocean but don't spawn. They
stay in the freshwater one season and return to the sea. The timing of the steelhead
returns to the ocean can vary even within the same stream.
Steelhead are classifield as two types based on the state of sexual maturity at the time
they enter a river and the duration of spawning migration. They are either
stream-maturing or ocean-maturing. The stream maturing type are called summer-run
steelhead. They enter the rivers of the Pacific in a sexually immature condition
between May and October. These steelhead require several months to mature and
The ocean maturing type, called winter-run steelhead, enter the freshwater rivers and
streams between November and April. They spawn within a short time. You will find
that the coastal streams of the Northwest Coast and the northern California coastline
are usually winter-run steelhead. The inland runs of steelhead that travel long
distances up the Columbia River are mostly summer-run steelhead.
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