What is a Steelhead Trout?

Did you ever go fishing at a lake or in a stream and catch a rainbow trout? Maybe you took some home to cook and eat or perhaps you practiced catch and release techniques. Well, these beautiful, speckled fish have a bigger version of themselves – the steelhead trout! Many people believe that steelhead and rainbow trout are different species, but in fact, they are the same and share the same scientific name (Oncorhynchus mykiss)!

Image by Joshua Gruver

Steelhead are the anadromous form of rainbow trout. This means they migrate from saltwater to freshwater to spawn in rivers. These fish return to the same streams they were hatched from, year after year! Steelhead are native to the Pacific coasts of North America and Asia. In many places around the world, they have been introduced into inland lakes and reservoirs for sport-fishing purposes.

Blue-green shading is present along the dorsal (back) side with black or dark green-colored spots running the length of the body and along the tail. The inside of their mouth and the belly is white in color. When an adult steelhead is returning from the ocean they are very silvery in color.

As they spend more time in freshwater preparing to spawn, they begin to look more like regular rainbow trout. Since steelhead have been in the ocean all year they have access to a larger food source and grow much larger and strong than their counterparts.

Image by Joshua Gruver

Most steelhead return to their natal rivers in the fall and winter. Some rivers support spring-run populations also. One distinction between salmon and steelhead is that steelhead can return to the ocean after spawning and return another year. Chinook Salmon will die after spawning and are unable to return a second time.

In the Eel River, which is California’s third-largest watershed, we have a fall/winter run of steelhead and another in spring. This beautiful area is surrounded by towering redwood trees and forest floors covered in ferns. It looks similar to scenes from the movie Jurassic World (actually some of it was filmed up here)!

Many years ago, logging activities, culverts, and placement of dams destroyed or degraded a lot of the available habitat for these fish. Many years of restoration efforts have taken place and now many scientists, like myself, are studying populations of these fish to see if they are recovering.

Image of a sonar camera setup by Joshua Gruver

Most recently I worked on a project where we placed a sonar camera in a section of the river. Sonar is a little soundwave that is sent out from a camera. When it “sees” an object in the water, the sound bounces back and a computer creates an image to review. We operated the camera 24 hours a day 7 days a week from November to March.

Scientists reviewed the sonar and counted each individual fish passing upstream and downstream on the journey to their natal stream for a suitable place to spawn. That information is used to estimate populations of fish over time and make informed, science-based decisions on how to help manage a recovering population of fish!

Now you can tell your friends about the differences between rainbow trout and their larger counterparts! Stay up to date with the CritterFacts newsletter and find my author page to learn more about fish, wildlife, and their habitats!