Juvenile steelhead lost to disease at Ringold Springs Hatchery

Image for post
Image for post
The parasite Ichthyophthirius multifilis as seen through a microscope.

A fish disease detected at the Washington Department of Fish and Wildlife’s (WDFW) Ringold Springs Hatchery in Mesa, north of the Tri Cities, recently resulted in the loss of a substantial number of juvenile steelhead.

About three-quarters of the 198,000 hatchery steelhead at Ringold were lost to “ICH” (Ichthyophthirius multifilis), a parasite that attaches to fish and affects skin and gills.

After detecting the disease in December, hatchery crews treated the 2.5-acre rearing pond holding the steelhead. However, conditions did not improve after a week and fishery managers decided to release the remaining 50,000 steelhead early into the cooler waters of the Columbia River to give them a better chance of survival, said Brian Lyon, regional hatchery manager for WDFW.

The disease was also detected in coho salmon and rainbow trout rearing in separate ponds at the facility, but treatments to those populations were successful, and very few fish were lost, said Lyon.

“The good news is the coho salmon and rainbow trout populations look healthy after hatchery crews treated those fish,” Lyon said. “Unfortunately, a combination of factors including warm water in the pond, allowed the parasite to thrive in the pond with steelhead despite the treatments.”

It has been about ten years since the parasite was last detected at the facility. Although the source of the parasite is unknown, Lyon said it was likely brought in from an outside source, such as river otters and birds looking for a meal. Despite deterrents at the facility, those predators sometimes find a way into the rearing ponds or water source.

Ich will cause less mortality in cooler waters of the Columbia River, where the parasite is already present. Because of this, the steelhead that were released are not expected to harm other fish species.

The steelhead lost would have been released into the Columbia River this spring and contributed to fisheries beginning in 2021.

Fishery managers are reviewing the incident to determine whether measures can be put in place to prevent a re-occurrence.

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store