Fish virus giving headaches to humans at Leaburg Hatchery.

Byline: INSIDE THE OUTDOORS By Mike Stahlberg The Register-Guard

Talk about a virus that just won't go away. Leaburg Hatchery manager Tim Wright finds himself - for the fourth time in as many years - battling infectious hematopoietic necrosis (IHN), a virus that attacks the kidneys of trout.

Rainbow trout in two of the hatchery's ponds - a total of 30,000 fish - tested positive for IHN in mid-November.

This after the hatchery shut down in July so its rearing ponds could be drained and "resealed" to prevent migration of the virus from pond to pond via groundwater.

And when Leaburg Hatchery reopened this fall it was definitely not business as usual.

"We made numerous changes," said Wright. "The major one being that we're not starting any fish here anymore. Typically, we start one-third of our total production from eyed eggs."

The trout now being reared were also brought later than normal, so they would be larger when first exposed to the McKenzie River water that flows through the hatchery.

That water is believed to carry the IHN virus, which is picked up in the ocean by summer steelhead and shed into the upper McKenzie when those steelhead return to spawn.

"We figured that at a larger size they'd have a more well-developed immune system," Wright said.

"We also changed some of our ongoing practices so as to put less stress on the fish," he said. "But we still have to mark (fin-clip) them, and maybe just the handling of the fish to mark them was enough to trigger the outbreak."

Leaburg Hatchery has been the Oregon Department of Fish and Wildlife's largest producer of "catchable trout." So when it catches a virus, local fishing catches a cold.

The biggest impact was in 2003, when trout releases dropped 30 percent below normal in Northwest Oregon due to losses at Leaburg.

Wright, ever the optimist, hopes the IHN will not spread beyond the two rearing ponds. If it doesn't, the Northwest Region's trout production goals will still be met.

State hatchery managers hedged their bets by cutting the number of fish being reared at Leaburg - normally about 700,000 rainbow trout - and shifting some of the production elsewhere.

"All we're rearing now is about 330,000," Wright said. About 250,000 of Leaburg's normal allocation is instead being raised at Willamette Hatchery in Oakridge. Another 100,000 are at Cole Rivers hatchery near Medford.

Wright says he's "still going to be confident" that there will be a full allotment of trout to release in area waters next spring and summer.

"I think we're going to get through this," he said. Most of the trout hatcheries, including Leaburg, started out with more fish than really needed "just to cover contingencies," he said.

Obviously, however, a long-term solution is needed.

Finding another water supply would be ideal. But engineers say drilling a well would provide only about 10 percent of the 4,500 gallons per minute that the hatchery draws from the McKenzie.

One other option would be to prevent steelhead - and, hence, the IHN virus - from moving above Leaburg Dam. That would be difficult, even though the two fish ladders at the dam could be used to trap steelhead. The problem is that steelhead begin arriving during the peak of the federally protected wild spring chinook salmon run.

A third option is to sterilize the water before it reaches the hatchery.

One method of purifying the water supply, Wright said, appears to be an ultraviolet disinfection system that kills any pathogens, viruses or parasites in the water.

Discussion of such a system, he said, "is on the table, but the cost is pretty steep - probably in the neighborhood of $1 to $2 million to install." Operating costs - electricity and periodic replacement of the ultraviolet lamps - could run $100,000 per year.

Doing nothing, however, is likely to leave Western Oregon anglers feeling sick about lost opportunities.

Mike Stahlberg can be reached at [e-mail].