IHNV is a naturally occurring virus found throughout the Snake River Basin. Some fish carry it for their entire life without any health problems. However, it can sometimes cause significant mortality when virus numbers in the water supply are high or fish are stressed, such as during the muddy, flooding river conditions which occurred this spring.

According to hatchery manager Ron Harrod, the source of the virus was most likely adult steelhead present in the Wallowa River above the hatchery. The Wallowa River is one of two water sources used by the hatchery.

The impact of the loss on fishing opportunities should be minimal, Harrod said.

“We will continue stocking fish according to schedule using trout from other hatcheries throughout the state,” he said. Most of the trout raised at the hatchery were destined for nearby Wallowa Lake.

While IHNV is common in waters of the Snake River Basin, ODFW policy does not allow the release of infected fish into water bodies that are virus free. This policy ensures that the Department protects natural and hatchery fish resources throughout the state.

IHNV is not harmful to humans. It is safe to handle or eat hatchery fish that already have been stocked, Harrod added.

As a result of the virus outbreak, the hatchery will cut its trout production from 50,000 fish per year to 20,000, raising those fish using a second water source where IHNV has not been detected. The other 30,000 fish will be raised by other hatcheries and released in Wallowa Lake. The recent outbreak will have no impact on the adult steelhead program at the hatchery.

Long term, the impact on the trout rearing program at the hatchery will depend on whether the virus returns to undetectable levels in the hatchery’s water sources.

News Source: Oregon DFW - Jun. 27, 2011