Good news: Researchers closer to getting handle on whirling disease

By SCOTT McMILLION, Chronicle Staff Writer

There's an old adage that often comes up when people talk about water-quality problems.

"The solution to pollution," the old saying goes, "is dilution."

And some of that philosophy can be applied when it comes to whirling disease as well, according to Dick Vincent, who coordinates research on the fish malady for the Montana Department of Fish, Wildlife and Parks.

"When the volume of water increases, the infection intensity decreases," Vincent wrote in a recent scientific paper, a document that outlined research both in a laboratory and in the Madison River, where whirling disease has taken a big toll on rainbow trout.

While that piece of information sounds promising, there's a great big catch to it, especially on the blue-ribbon Madison.

"It's going to take a lot of water" to get enough dilution, Vincent said in an interview this week.

The Madison doesn't always have enough water and, when it does, it's often stored in reservoirs to ensure a steady supply for electrical power and other needs.

Tiny trout are the most susceptible to whirling disease and, on the Madison, where rainbows emerge late in the spring, the most critical period is from June 15 to July 15.

Tubifex worms are shedding parasitic spores at that time, spores that attach themselves to young trout and deform the head, causing the fish to lose equilibrium and sometimes spin in circles, giving the disease its name.

However, it takes about 200 to 300 attached spores to seriously damage a fish, Vincent said, and with more water, there's less chance of that happening.

The upper Madison's average flow in that time is about 12,000 to 15,000 cubic feet per second. Vincent said it would take about 25,000 cfs to significantly reduce the severity of the disease.

"That's more than you could realistically expect to see in the river in that time frame," Vincent said. "I mean a lot more."

The Hebgen Lake Dam near West Yellowstone stands upstream from the study area.

That dam generates no electricity, but stores water needed later in the year for downstream dams. PPL Montana owns the dams.

"It would cost them money" to release the water, Vincent said. "We can reduce infection rates, but at what cost?"

There are other concerns as well, according to John VanDaveer, manager of hydro resources for PPL.

If Hebgen releases too much water, it could erode the natural dam at Quake Lake, he said. Plus, recreation on Hebgen Lake demands a full pool. Generating electricity is the third priority for Hebgen Dam, he said.

And with the ongoing drought, it's difficult just to fill the dam and meet minimum flow requirements without boosting them, he said.

Dave Kumlien, executive director of the Whirling Disease Foundation, said that even if Vincent's research can't be applied to the Madison, it could be critical in other streams affected by dams or irrigation.

Vincent agreed. In small streams where the disease thrives, changing flows by even a small amount, and at the right time, could make a big difference.

"It might not look like much, but it's enough," Vincent said.

Other research is progressing, Kumlien said, including work with different strains of rainbow trout that seem more resistant.

But the main focus is on trying to reduce the severity of the disease, rather than try to eliminate it.

However, in dry years, finding extra water can make that hard to do.

"In drought years, whirling disease is going to worsen," Vincent said. "Because all streams have less water."

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