steelhead 4.29

The steelhead on the left is a repeat spawner. Such fish make more than one trip between their home water and the Pacific Ocean.

Spring is spawning season for Idaho’s steelhead.

These fish make an incredible journey to reach their home streams to spawn. Sometimes it is not their first trip home.

Young steelhead live in Idaho for one to five winters. When they get big enough they make their way to the ocean where they pass eight dams in the Snake and Columbia rivers. In the ocean, steelhead swim immediately offshore, sometimes as far as the Kamchatka Peninsula in Russia on the far side of the North Pacific. When they return to Idaho, they have to swim farther and climb higher than any other steelhead, passing the same eight dams again.

For some steelhead, the journey doesn’t stop there. Unlike salmon, steelhead can survive spawning and return to the ocean. If they survive in the ocean and return to spawn again, they are called repeat spawners. At that point they will have passed a dam 32 times in their lives. Outwardly, they look like any other steelhead, but the stress of spawning leaves marks like ragged scars on their scales. If they are tagged with a PIT-tag, detection of that tag allow them to be tracked on their second spawning migration.

One such fish was tagged on July 22 as a youngster, not quite 4 inches long, in the South Fork Salmon River. Almost two years after tagging this steelhead was detected moving downstream past Lower Granite Dam in the Snake River on May 6. Another two years later, it returned from the ocean on Sept. 3 as an adult and swam to Idaho to spend the winter. The following April it was detected heading upstream in the South Fork Salmon River. A month later, the steelhead was detected moving downstream past the dams in the Snake River. It spent another four months in the ocean and returned again. It entered the fish trap at Lower Granite Dam and was 29 inches long.

This repeat spawning steelhead was last detected in late April back in the South Fork Salmon River, having lived seven years. This fish, while rare, was not alone on its adventure. Idaho Fish and Game personnel estimate 1 to 2 percent of the steelhead that come back to Idaho in a given year are repeat spawners. A few steelhead that have completed three spawning migrations have been tracked.