Colorado researchers spent decades trying to save disappearing rainbow trout. Finally, they’re making progress — The #Colorado Sun

In the Gunnison River gorge, CPW Aquatic Biologist Eric Gardunio, holds a whirling-disease resistant rainbow trout. CPW is stocking fish resistant to the disease throughout the state. Photo credit: Colorado Parks and Wildlife

Here’s an in-depth look at CPW’s efforts to recover Rainbow trout from Kevin Simpson that’s running in The Colorado Sun. Click through and read the whole article for the photos and details about the disease. Here’s an excerpt:

Genetics from Germany and a hardy cross with Gunnison River trout seem to be overcoming a nightmarish parasite that causes deadly whirling disease

Through dogged research that called on experts throughout the U.S. and even Europe, the rainbow has staged a remarkable recovery that required years of genetic testing, cross breeding and painstaking reintroduction into Colorado’s waters. Only recently have those efforts shown signs of enduring success against the parasite that nearly destroyed it.

And in large part, it has been developments in the rugged Gunnison River waters, where researchers cultivated a strain of rainbow — dubbed the HXG — that’s both disease-resistant and hardy enough to survive in the wild, that have pushed the effort toward sustainability.

More than 1.3 million of the new fish will be introduced into Colorado’s waterways this summer.

“It’s been an ongoing sort of thing, an evolution of little successes over time,” says George Schisler, chief of aquatic research for CPW and one of the key players in the long-running drama. “Now that we’ve got a lot of these HXGs in production, that’s the tipping point. We’re starting to see more and more little rainbows surviving in the wild.”

To get here, the fish beloved by anglers for its colorful appearance, relative ease to hook and admirable fight, had to overcome a nasty parasite, hungry browns and a whole lot of trial and error…

The department’s electrofishing along a 2-mile stretch of the Colorado near Kremmling in 1993 shocked well over 1,000 fish to the surface. Nehring recalls counting a huge population of wild rainbows from 16 to 24 inches long — but only five under 12 inches.

It was a mystery what happened to the little ones. The results of the count were nothing like they’d seen on that same stretch of river in the early ‘80s, when there were plenty of big rainbows, but most fell in the 9-inch range — evidence that the young ones were thriving.

At the same time, the brown trout population was virtually unchanged over that period. Nehring looked everywhere for possible culprits: water temperature, flow fluctuations during rainbow spawning and egg incubation, pollution, floods. But he could find no factors that seemed to make sense. That stretch of the Colorado seemed to be missing two years’ worth of wild rainbow trout fry — recently hatched fish — with no similar impact on the browns.

When Nehring called in to report the conundrum, his boss wondered if the answer might be something called whirling disease that plagued tiny rainbows but not browns.

“At that time I didn’t even know what whirling disease was,” Nehring says.

Although the life cycle of the parasite — Myxobolus cerebralis — has been understood only since 1984, whirling disease dates its discovery to the late 19th century at a trout farm in Germany. Scientific literature was sparse. In Colorado, a state fish pathologist determined after testing some infected rainbows that there was less than a 5% chance that whirling disease was responsible for the disappearance of the young rainbow population…

Although Nehring sounded the alarm, most fish and wildlife experts didn’t pick up on the damage that whirling disease was doing to the state’s rainbow trout population until years after they’d studied bottom-feeding tubifex worms. The worms, which live in the mud and sediment of river and lake beds, had proved unwitting distributors of the spores that infected young fish and fed on the cartilage that later would mature into bone.

The result is a misshapen skeletal structure, with deformities that include a telltale lateral curvature of the spine. Eventually, inflammation causes nerve malfunction. The result is a rainbow that whirls in endless circles, and either dies of the infection or becomes prey — often to the large population of brown trout. Cutthroat and some other species are vulnerable to the disease, too, but rainbows are particularly susceptible.

#Drought news: Temperatures from 3 to 12 degrees above normal common in W. #Kansas, W. #Nebraska, and in E. #Colorado and #Wyoming in the last week

Click on a thumbnail graphic to view a gallery of drought data from the US Drought Monitor.

Click here to go to the US Drought Monitor website. Here’s an excerpt:

This Week’s Drought Summary

This week, dry conditions were common across parts of the central and southern Great Plains, as well as parts of the northern Great Plains, particularly in North Dakota. Dry conditions were also common in much of the Intermountain West. However, above-normal rainfall occurred in eastern Washington, as part of an unusual severe thunderstorm event in Washington and Oregon on Saturday. Near or slightly below normal temperatures were found across much of the central and south-central continental United States, while warmer than normal temperatures (with some locations reaching between 5 and 15 degrees above normal) were common in the western High Plains and the West. Meanwhile, dry conditions also occurred along the northeastern Atlantic Coast. Above-normal rainfall fell in south Texas, central and south Florida, and parts of South Carolina and North Carolina. Moderate, severe, and extreme drought expanded in parts of the southern and central plains where high evaporative demand and paltry precipitation continued. Elsewhere, drought conditions also spread or lessened in parts of the West, where recent precipitation or lack thereof either improved conditions or caused conditions to dry out further. Minor changes in moderate drought were also made east of the Great Plains; for more details on these, please see the regional paragraphs…

High Plains

Warm and dry weather encapsulates the conditions across most of the High Plains this week, particularly in the western part of the region. Temperatures in the eastern part of the region were generally moderate, but temperatures from 3 to 12 degrees above normal were common in western Kansas, western Nebraska, and in eastern Colorado and Wyoming. Below-normal precipitation occurred in most of South Dakota and North Dakota, and primarily to the west of the U.S. 81 corridor in Kansas and Nebraska. Above-normal rainfall fell in parts of eastern Kansas, and a small area of above-normal rainfall also occurred west-northwest of Omaha, reducing the coverage of abnormal dryness in the Bohemian Alps and Platte River Valley areas of eastern Nebraska. Abnormal dryness expanded through much of central and eastern Wyoming to parts of northwest Nebraska and the Black Hills and Badlands in southwest South Dakota, due to increasing short-term precipitation deficits and, in Wyoming, high evaporative demand over the past month. Moderate drought increased in coverage along and north of the Missouri River in northwest North Dakota, where short-term precipitation deficits continued to build, and surface water shortages were indicated. In southeast Colorado and a small part of adjacent southwest Kansas, extreme drought expanded, as short-term precipitation deficits continued to worsen amid high evaporative demand…


Warmer than normal temperatures were widespread in the West this week, particularly in the Intermountain West area, where temperatures 9 or more degrees above normal were commonplace. Below-normal precipitation in southwest Colorado and in parts of Utah, Wyoming, and Montana led to degradations in conditions. Severe drought increased in coverage in southeast Utah and southwest Colorado, where short- and long-term precipitation deficits continued to build amid high evaporative demand. Short-term precipitation deficits led to an increase in moderate drought coverage in southwest Montana. As mentioned in the High Plains paragraph, large evaporative demand and inadequate precipitation led to the development of widespread abnormal dryness across much of central and eastern Wyoming. Meanwhile, above-normal precipitation in eastern Washington and parts of north-central Oregon, where a localized severe weather event occurred on Saturday, led to improved conditions as precipitation deficits lessened. Also as a result of recent precipitation, extreme drought coverage lessened in southwest Oregon…


Conditions in the South this week varied widely from east to west, leading to primarily improving or unchanged conditions in the eastern part of the region, and degrading conditions in the west. Like the Southeast, most of the South had temperatures this week between 5 degrees above and below normal; however, notable exceptions on the warm end of this occurred in parts of the Texas and Oklahoma panhandles. Scattered areas of above- and below-normal rainfall dotted the region generally to the east of Interstate 35. Moderate drought slightly increased in coverage in a small area of southern Mississippi, where paltry rainfall occurred this week. Improvement in drought and abnormal dryness areas was common in south Texas and along the Texas Gulf Coast, where rainfall this week was mostly above normal. Areas of moderate and severe long-term drought slightly shifted along the Rio Grande, while otherwise degradation was quite common in West Texas and the Texas Panhandle. Extreme drought developed in the Oklahoma Panhandle, and adjacent areas of the southern and central high plains, where conditions had become extremely dry in the short-term as a result of low precipitation and high evaporative demand. Severe drought was also introduced in a small area northwest of Oklahoma City, where short-term precipitation deficits had worsened…

Looking Ahead

As of the afternoon of Wednesday, June 3, the National Weather Service Weather Prediction Center is forecasting dry weather to continue over the southern Great Plains and the central and southern high plains from June 4 to the evening of June 8. Heavy precipitation is possible from the central Gulf Coast eastward into the Florida Peninsula. Through the evening of June 10, heavy precipitation is also possible in the Mississippi River Valley, as well as eastern portions of Nebraska, North Dakota, and South Dakota. Some of the forecast rainfall will likely be dependent on the evolution of Atlantic tropical cyclone Cristobal. Please monitor forecasts from your local National Weather Service office and the NWS Weather Prediction Center for rainfall forecasts and for information on possible hydrological impacts from Cristobal. For the latest information on Cristobal, please refer to information and forecasts from the National Hurricane Center. The Climate Prediction Center is forecasting increased chances for warmer than normal temperatures in California and across southern New Mexico, Texas, Louisiana, and the southeast Atlantic and Gulf Coasts for June 9-13. Meanwhile, near-normal or below-normal temperatures are forecast over much of the rest of the continental U.S. during this period. Increased chances for above-normal precipitation are forecast in the eastern and central United States as well as in the Pacific Northwest, while increased chances for below-normal precipitation are forecast in the High Plains, Texas, Oklahoma, and the Rocky Mountains.

Here’s the one week change map ending June 2, 2020 from the US Drought Monitor.

US Drought Monitor one week change map ending June 2, 2020.

And, just for grins here are early June US Drought Monitor maps for the past few years.

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