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DENVER (AP) – The Colorado Division of Wildlife hopes a new policy on a crippling fish parasite that has invaded most of the state’s rivers will calm troubled waters – eventually.

State officials, though, concede the decision to quit placing lightly exposed fish in some waters could make waves for a while because there will be fewer fish to stock.

That worries business owners who rely on fishing. Whirling disease has been blamed for plunging numbers of rainbow trout, considered the prize catch in Colorado’s $1 billion fishing industry.

State officials insist recreational fishing hasn’t been affected because there are enough brown trout resistant to the parasite that causes whirling disease to fill the vacuum. For anglers who prefer the rainbows, however, the loss of the bigger and more aggressive fish hurts.

“It’s just sad. It’s losing-an-old-friend type of thing,” said Breckenridge fishing guide Jackson Streit.

Since whirling disease was confirmed in Colorado in 1987, the number of young adult rainbows has dropped by 90 to 95 percent in some of the state’s best trout rivers: the Cache la Poudre and parts of the Colorado, Gunnison and South Platte.

The whirling disease parasite spread to 13 of Colorado’s 15 major river drainages after infected fish from a private hatchery in Idaho were released. It also infiltrated state hatcheries.

To keep fish numbers level, the Division of Wildlife, using precise DNA testing not used by other states, has stocked lightly infected fish in some waters. That will stop in 2003.

Exposed fish still will be put in lakes and streams on the eastern plains, but only disease-free fish will go in trout habitat: cold-water streams and lakes in the mountains.

That could mean fewer stocked fish, but Colorado Trout Unlimited welcomes the change it hopes will wipe out the disease.

“The policy is certainly, in our opinion, overdue. We would have liked to have seen this step taken a long time ago,” said David Nickum, the conservation group’s executive director.

It isn’t just a matter of recovering the rainbow population, he said. Biologists don’t want to see the disease infiltrate the habitat of native cutthroat trout, gone from much of their historic range.

Colorado State University fish-science professor Harold Hagen thinks the state is wasting millions of dollars fighting the parasite.

“No one has ever proved conclusively that whirling disease is causing all of these mortalities,” Hagen said.

Even if the disease is the cause, raising fish in sterile hatcheries will keep them from developing natural resistance, he said.

State researcher Barry Nehring, a national expert on whirling disease, conceded that habitat condition and other factors may be affecting rainbow trout, but biologists think whirling disease is a main culprit. Breeding disease-resistant fish may be years in the future, he said.

Young fish are particularly vulnerable to the infection, which attacks the cartilage and nervous system, leaving fish deformed or spinning in circles.

The parasite begins life as a spore capable of living in soil for 30 years. When an infected fish dies, the spores are released and attach to other fish or are eaten by bottom-dwelling worms, the parasite’s host. Fish also can be infected by eating the worms.

Salmon and rainbow trout, native to the United States, are the most affected. Brown trout are more resistant to the parasite, possibly because they were exposed to it in their native Europe. They still carry the spores.

Whirling disease, which isn’t a threat to humans, has been confirmed in 23 states, in the Northeast and throughout the West, where it has taken the largest toll.

Nickum said Wyoming, Utah, New Mexico and Montana always refused to stock infected fish.

Colorado’s early decision to keep stocking infected fish was “a big, big mistake,” said Eddie Kochman, manager of the state’s fisheries.

“Colorado got hit with it before any other Western state. We knew nothing about it,” he said.

Nehring’s research shows that even lightly infected fish can spread the disease, Kochman said.

Disinfecting water lines and switching from surface to ground water at hatcheries have helped reduce the level of infection, said Eric Hughes, chief of hatchery production.

Nine state hatcheries have been certified free of the parasite, and four are being modernized. The other three will likely never be disease-free and will be used to stock waters in eastern Colorado that aren’t conducive to fish reproduction.

Once lightly infected fish can no longer be stocked in mountain waters, it will be difficult to produce enough fish to keep up current levels, state officials said. The state will have to buy more fish from private hatcheries.

The Wildlife Division estimates it can produce about 3.5 million fish in 2003. The state produced an average of 4.68 million fish annually before whirling disease.

“I don’t think they’re going to meet their quotas,” said Greg Austin, president of the Colorado Fishing Federation.

Meanwhile, the state wants to raise license fees, he said.

“They’re putting less product out there for a higher dollar, so a lot of people have just quit fishing,” Austin said.

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