Ash and debris carried by heavy rains from the 416 fire burn scar into the Animas River north of Durango suffocated thousands of fish, Colorado Parks and Wildlife officials said.

“We’re seeing thousands of fish struggle for their last gasp of air on the river 10 to 15 miles north of Durango, likely down into New Mexico,” said the spokesman for the Southwest Region of Colorado Parks and Wildlife Southwest, Joe Lewandowski. “We can’t even get an exact number because the river is so dark and brown, and we can’t do much about it until the runoff flushes out.”

Lewandowski added that the Animas River has not seen such a massive die-off from wildfire debris runoff in recent memory, though the Missionary Ridge fire wiped out the fish population in the Florida River northeast of Durango in 2002.

The hardest rains hit areas of the 54,129-acre burn scar about 5 p.m. Tuesday, the Durango Herald reported. The flooding and debris flows forced the closure of U.S. 550 and halted the Durango and Silverton Narrow Gauge Railroad train. About 400 passengers were shuttled off the train, and about 200 campers at the KOA near East Animas Road were bused to the La Plata County Fairgrounds.

Wildlife officials and members of the public are primarily finding dead rainbow and brown trout as well as flannel mouth and bluehead suckers. The flannelmouth and bluehead suckers are of particular concern, since the two species are native and endemic to the Colorado River basin.

“They’re very hearty fish that have endured huge runoffs, low water levels, high temperatures and a variety of other pressures,” Lewandowski said. “But we’re not sure how they’re going to do with this type of ash and debris runoff because we’ve never seen anything like this.”

Parks and Wildlife’s first gauge on the severity of the fish kill will likely come in September.

Biologists plan to conduct a fish survey in 6 miles of the Animas River that run through downtown Durango in which they electroshock the fish and record their numbers, weight, size, species and other observations.

“You never know, fish are pretty good survivors if they are able to find a seep of fresh water or a spring,” Lewandowski said. “We’ll only be able to get a sense of that in September, though.”

The fish in the Animas River showed off their survival skills most recently after the Gold King Mine spill in 2015. The Environmental Protection Agency did not report any major fish kills after workers accidentally destroyed the plug holding wastewater trapped inside the mine, despite the deluge of heavy metals such as cadmium and lead and toxic elements such as arsenic, zinc, iron and copper into a tributary of the Animas River that turned the water a bright yellow/orange.

Lewandowski said the fish were saved because river was flowing at a high enough level to dilute the toxic metals and maintain enough oxygen in the water for the fish to survive, though there are likely longer term consequences for aquatic invertebrates.

At the time of the spill, the river was running at 1,000 cfs. This week’s storm boosted the river’s flow to 462 cfs midday Wednesday, though from July 11-17, the river was flowing between about 225 and 325 cfs.

Fish in the Animas River have battled toxic metals from the Silverton-area mines for hundreds of years. Lewandowski said the fish population in the river is not naturally sustaining, so it is periodically restocked with trout from hatcheries all over the state.

“You can look at the river and, though it’s perfect clear, we are seeing positive results for copper, zinc and other metals that get into the fishes’ sensitive system,” Lewandowski said. “The good thing about the mine spill is that it triggered a large awareness across the country about the acid drainage problem from mines all over the country. It was a tough way to start, but it certainly got people’s attention and made them look more critically at river systems.”

Colorado Parks and Wildlife is taking precautions to protect Rio Grande cutthroat trout in the watersheds threatened by runoff from the 108,045-acre Spring Creek fire near La Veta. Lewandowski said biologists are collecting the endemic fish and moving them to the Monte Vista Fish Hatchery to serve as a broodstock for spawning next spring.

“We do what we can with the resources we have available to make sure we minimize the impact of anything that could affect population size and diversity,” Lewandowski said.

Twitter: @lizmforster Phone: 636-0193

Twitter: @lizmforster

Phone: 636-0193

Liz Forster is a general assignment reporter with a focus on environment and public safety. She is a Colorado College graduate, avid hiker and skier, and sweet potato enthusiast. Liz joined The Gazette in June 2017.

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