Missoulian via Associated Press

ARLEE, Mont. (AP) -- Some of the rainbows in the public viewing area at the Jocko River Trout Hatchery weigh as much as 20 pounds, and measure in just four inches shy of three feet long.

Yes, we're talking huge.

Drop a pellet of food in the water, and you're likely to get wet as the nearest dozen or so of the fish race toward the surface, where only one can claim the snack.

"It's a jungle in there," says hatchery manager George Kirsch which is the primary reason Kirsch and his staff spend so much time making sure many of the fish they plant in western Montana lakes, rivers and ponds can't reproduce.

"It's always a concern that hatchery fish may interfere with the wild population," Kirsch says. "Hatchery fish are more aggressive. They don't just compete with wild fish, they can manhandle them."

It's a trait you don't want introduced into the wild population, Kirsch says, and while there's no evidence that happens, Montana Fish, Wildlife and Parks prefers to err on the side of caution.

So Kirsch and his staff perform the equivalent of vasectomies and tubal ligations on the rainbows.

They've gotten pretty good at it.

They can do 100,000 of the procedures an hour.

Of course, no one's snipping or sewing anything. The fish are made sterile while they're still in egg form.

There are two ways to do it, applying either heat or pressure to the eggs. Either way turns a diploid, or an embryo with two sets of chromosomes, into a triploid, or one with three sets.

Those with three can't reproduce.

The heat method is less effective, and so here at the Jocko River Hatchery, they use pressure.

It's quite a process, timed literally to the second, and begins the moment the eggs are fertilized.

"We hit the stopwatch button the second the sperm hits the eggs," Kirsch says.

From there, everything is based on water temperature. Kirsch and his staff have developed a chart based on the water being 50 degrees, which means the eggs have to be in the pressure chamber, locked, loaded and airtight, and the pressure built up to 9,500 pounds per square inch, exactly 32 minutes after being fertilized.

If the water is warmer, it has to be done quicker; if it's cooler, they may have a minute or two longer.

"The cooler the water temperature, the slower the development," Kirsch explains.

"It's a pretty rigid timeline," he goes on. "It takes 45 seconds to build the pressure to 9,500 pounds" in the chamber, so it must be loaded with fertilized eggs and water, sealed and fired up exactly 31 minutes and 15 seconds from the time sperm meets eggs.

They can do 25,000 eggs at a time.

In addition, each egg develops at its own speed, one of the potential obstacles to 100 percent sterility.

"The most precocious egg may hit the right point in 31 minutes," Kirsch says. "The slowest eggs, or those predisposed to being slow, may need 34 minutes."

In both cases, there's a five-minute window to get the sterilization done without killing off too many. The process "shocks" the eggs at just the right point, causing them to form three sets of chromosomes instead of two.

"We've tried to pin down the perfect time where we get every egg sterilized," Kirsch says. "Within that five-minute period, putting them in when they're 32 minutes old, we get the ones that take 34 minutes but the fastest are still covered, too. The trick is not just

100 percent sterility, it's to do it without increasing mortality, too."

The hatchery has about an 85 percent survival rate with eggs it doesn't sterilize, and is pretty close to that 80 percent with the ones it does.

FWP's primary goal, Kirsch says, is to not interfere with the wild population while improving the state's fishing resources.

Places such as McCormick Pond in Missoula, Beavertail Hill Pond, Harper's Lake and Ninepipe Pond, a "pothole" lake near the Ninepipe Reservoir, are examples of places where hatchery rainbows that haven't been sterilized can be placed. They can't get out and interact with wild populations.

But someplace like Lake Como in the Bitterroot, that's another matter.

"Como is a place we need to plant rainbows because it won't sustain a population," Kirsch says, "but there's always a chance a few might get through the dam and into the Bitterroot River and its tributaries."

It's places like that where the triploids that cannot produce offspring are planted.

Idaho Fish and Game introduced the pressure process to Montana Fish, Wildlife and Parks, but it's Kirsch and his staff who have gone through the trial and error to make it work here.

"I'm not Al Gore, I didn't invent the Internet," Kirsch says, "but we took what they did in Idaho, applied it to our situation, our fish, our water temperatures, and set up the research and made it as idiot-proof as we could. We adapted other people's hard work to our purposes."

The Jocko River Fish Hatchery has run about 6 million eggs through the pressure chamber each year since the program began in 2006. Most are shipped to other hatcheries in Montana, and about 400,000 are planted in western Montana, most two years after their five minutes in the pressure chamber.

A native of Pennsylvania, Kirsch came West to obtain his master's degree at the University of Montana, and has worked for FWP at hatcheries ever since first at Washoe Park Trout Hatchery near Anaconda, then at Bluewater Springs Trout Hatchery outside Bridger and Murray Springs Trout Hatchery in Eureka, where he and wife Beverly spent the bulk of Kirsch's 30-year career raising their two sons, Dan and Jonathan.

They've been in Arlee since 1999, living in the home at the hatchery that comes with the job among all their other duties, the three-person staff is responsible for security at the hatchery 24-7 but he won't be there much longer.

Kirsch, 55, is retiring from the "job I love." His last day on the Jocko is Saturday.

On June 6, he and Beverly move to Alaska, where both their sons and now, two grandsons live.

And, we hear, where the fishing is pretty good.

But Montana's isn't bad, either, and Kirsch says the state is lucky.

"We're fortunate to still have wild fisheries. Not every state does," he says.

The sterilization process, he adds, is one way FWP is "doing everything we can to keep it that way."

Copyright 2010 The Associated Press.

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