Whirling disease changed how hatchery raises fish | PostIndependent.com

Whirling disease changed how hatchery raises fish

JOHN GARDNERGlenwood Springs, CO Colorado
Post Independent/Kara K. Pearson

Whirling disease was first discovered in Colorado in the late 1980s, according to Rifle Falls Fish Hatchery Manager Dave Capwell. And even though the Colorado Division of Wildlife is still battling the disease in many waters around the state and nation, the Rifle hatchery has made gains in perpetuating a healthy stock of trout on the Western Slope.Around 2001, the Rifle Falls Fish Hatchery eradicated whirling disease from the facility, according to Assistant Hatchery Manager Mark Jimerson. One reason was a switch to using spring water rather than Rifle Creek water.”We isolated the spring water from Rifle Creek so that none of the contaminated creek water gets into the facility,” he said.The change cut the water flow by nearly two-thirds – from 40 cubic feet per second (CFS) to 15 CFS, according to Capwell – but ensured a clean water source to raise healthy fish crops.”A lot of hatcheries nationwide were affected by the disease,” Capwell said. “But today, we know for sure that the fish here are clean from everything.”

Twenty-two states nationwide have reported infected fish populations, according to the Whirling Disease Foundation’s Web site.The Rifle hatchery started an “isolation facility” mostly used for raising native cutthroat trout. The facility is separate from the rest of the hatchery and uses its own water supply from another natural spring producing approximately 1 CFS.The fish are raised and sent out for disease testing through a process called polymerase chain reaction (PCR), according to Capwell. PCR testing is a technique for sampling fish DNA to detect and diagnose infectious disease.The facility is separated into four different sections to provide separation of one species of fish from another. Separation ensures no diseases will be transmitted. The hatchery had to quit using original storage ponds built when the facility first opened because the soil was – and still is – contaminated with whirling disease, Capwell said.An infected fish crop could be destroyed, but they try to find other things to do with them.

“Normally we don’t destroy them,” Jimerson said. “We will put (infected) fish into whirling disease positive waters. We avoid destroying them if we can.”The isolation facility has improved the way the DOW breeds and raises fish nowadays.”The facility gives us the flexibility to go into the wild and help perpetuate the fish population,” Capwell said.For instance, Capwell said that wild brood stocks, wild fish used for breeding crops, have to be tested every three years. Testing requires a sample of 60 fish. In some instances, Capwell said, there may only be 40 or 50 fish inhabiting a certain drainage. The isolation facility allows them to bring in 10 fish from the drainage, breed and raise a crop to give them a sample for testing, then release the original 10 back into the drainage.”It doesn’t make sense to take the 50 out of the drainage and test them,” Capwell said. “Out of that 10 we can produce 4,000 and test from that section.”

If the tested fish are infected the DOW can eliminate the rest of the group from the drainage or lake. If the tested fish are determined to be disease free, they can be stocked and the rest of the crop may even be used to re-establish a population in a barren drainage, Capwell said.Contact John Gardner: 384-9114jgardner@postindependent.comPost Independent, Glenwood Springs, Colorado CO

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