Fried fish, smothered fish

How global warming is devastating Colorado’s native fish

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This summer, thousands of fish were found dead on the banks of the Animas River after the 416 Fire heated stream temperatures and polluted the water with ash and debris.
Ryan Votta

First thing every morning, Ryan Votta walks across the Durango Fish Hatchery campus and over to the isolation unit. Before stepping inside, he disinfects from his hands down to his shoes. “Biosecurity is a big issue,” he explains. “We can’t risk the chance of bringing in any kind of disease.”

Votta, the hatchery’s assistant manager, is checking in on a vulnerable Colorado-native cutthroat trout species the hatchery is protecting. They have about 50 juveniles and 100 eggs in their facility at the moment — all of which were rescued earlier this summer from the 416 Fire that ravaged Colorado’s southwest San Juan mountains. There, biologists have been able to trace the fish’s genetic lineage back thousands of years.

“Our fear was that fire would compromise [the native cutthroat trout],” Votta says. The 416 Fire, which burned over 55,000 acres in the San Juan National Forest throughout June and July, is now recorded as the sixth-largest fire in state history. Not only did its flames warm streams to temperatures fatal for the cold-water-loving trout, but its ash and subsequent debris polluted the water, making it impossible for fish to breathe.

Within days of the fire’s emergence, Jim White, Colorado Parks and Wildlife (CPW) aquatic biologist in Durango, knew he had to get into the burning forest and salvage what native San Juan fish he could — if only to collect and preserve a sampling of the unique subspecies. Trout specialize in their habitats, and populations in different streams across the state have evolved slight hereditary differences. “Trying to preserve genetic diversity across landscape is a priority for these fish,” White explains.

Besides, less than a decade ago, biologists once thought the San Juan native cutthroat trout subspecies was extinct, and White wasn’t going to let that happen for real on his watch.

So, for the first of two rescue missions, a team of biologists from CPW and a few hatchery employees with a U.S. Forest Service squad carved a path directly into the raging 416 Fire to a creek where they could collect specimen samples. Once the fire subsided a few weeks later, they re-entered the burn area to try saving more and to diversify their sampling.

As for the rest of the fish in the area that the team couldn’t rescue, they’re likely now all dead.

Joe Lewandowski
Fish found on the Animas River bank on July 18 likely suffocated due to ash and debris pollution from the 416 Fire.

On July 18, not long after the rescue missions, Joe Lewandowski, CPW’s southwest public information officer, stood on the banks of the Animas River, which flows out from San Juan National Forest and through Durango. Thousands of fish, he says, were lying there, dead, along the river bank.

“We picked them up and looked at them. Instead of a bright red like they usually are, they were brown because of all the dirt they were ingesting,” he recalls. “We can’t say for sure, but it was close to 100-percent fish kill [near the rescue area, a tributary of the Animas].”

The cutthroat trout is an iconic one for Colorado, being the state fish and a beloved subject of recreationalists across the West. But, according to White, the fish today only occupies 14 to 15 percent of its historic range in the Colorado River Basin. After the 416 Fire, their range is now further compromised.

“It’s not easy on fish,” White says of global warming and climate change. Going in to retrieve the native trout “were fairly dangerous missions, with the fire burning actively, yet this is a really cool conservation story to tell.”

The story of helping Colorado’s native cutthroat trout goes back a long way, White starts to explain as he gazes from his office window out to the Animas River, which still runs a slight chocolatey brown. “Back in the 1880s and ’90s a lot of our cold-water fish stocks were wiped out, by either mining or timber or hunting [interests] that just changed the habitat forever.”

As a result, non-native trout like brook trout, rainbow trout and brown trout were widely stocked across the state. As more aggressive fish, they dominated native habitats and species like the greenback cutthroat trout, Rio Grande cutthroat trout or the yellowfin cutthroat trout. Hybridization also occurred, further diminishing native populations, and for a long time it was difficult for scientists to differentiate between the multiple subspecies of trout that now roam the state’s waters.

Joe Lewandowski
Colorado trout today occupy only a fraction of their historic range.

But about five years ago, White explains, there was a major breakthrough: a genetic test that could finally distinguish between the subspecies. Researchers collected tissue samples from two 150-year-old Coloradan fish preserved in at the Smithsonian Museum, and compared them to different fish of today’s generations.

“That was really exciting,” White says. “We finally had this knowledge and a better understanding of which cutthroat were native to which basin.”

It was from these tests, that researchers determined the San Juan native cutthroat trout were extinct. “When they examined the specimens we’d collected … we couldn’t find any that matched the information [we had] at the time,” White says.

It was only about five years ago that researchers realized the software they were using “was masking the fact that these fish had a different genetic map to them,” White says, and San Juan native cutthroat trout reemerged in the spotlight. “So, yes, cutthroat trout that are aboriginal or native to the San Juans are alive. But the populations that have lasted are tiny and very vulnerable.”

Their habitat, for one, has been increasingly threatened as Colorado’s climate changes and grows warmer, even without the direct contact of forest fires. Low flows and warmer water translate to less oxygen available, which stresses fish all over the state. This led CPW to issue numerous voluntary fishing bans in rivers over the course of the summer.

“Our flows [on the Animas] are down 30 percent from 10 years ago,” Lewandowski says, for example. “It’s bad. It’s way down. Looks like today (Aug. 24) it’s running at about 161 cubic feet per second (cfs), and the average is 520 cfs this time of year.”

Joe Lewandowski
Ash and debris schlepped into water from forest fires can suffocate fish.

Lewandowski points at the year’s low snowpack for an explanation. “We had less than half of average snowfall [this past winter], and that’s the most significant factor. … Now that can change season to season, but overall we’ve had less snow in the last 10 years in the high country and that translates to less water. And when you have less water for fish, you have less habitat.”

On July 17, around the time of White’s and the hatchery’s second rescue mission, the Animas measured 300 cfs. It’s average flow that time of year should have been closer to 1,000 cfs, according to CPW.

Due to low flows, water temperatures have risen. Trout thrive around 60 degrees or lower, yet CPW reported Animas River temperatures above 70 degrees on several afternoons this summer. “Water temperature that high can cause fish to die. … Historical records for the river show that in mid-summer the Animas River averages 58 degrees,” a July 17 press release states.

Lewandowski adds, “Once you get above 65 degrees, you have less oxygen in the water. … It’d be like me and you if we only had 60 percent of the oxygen in the room. It can really cause die-offs.”

The implications of dying fish in Colorado is multifaceted. Animals like heron, mink and otters, for example, supplement their diet with trout; anglers and outdoor recreationists pour hundreds of thousands of dollars into the economy. Losing all the fish, “could throw everything out of balance up there,” Votta says.

“But one of the things that cutthroat trout represent to me,” says White, “is cold, clean water. As we lose these fish, as water becomes warmer and dirty from ash or debris, it’s yet another signal that water, which is a precious resource, is being impacted.”

Colorado’s native cutthroat trout are indicators of Colorado’s environmental health. “A river is nothing more than a reflection of its watershed condition,” White says. “And clearly, yeah, it’s frustrating. It would be nice to sustain these habitats. … Some rivers are just never coming back.”

As for how the native cutthroats are doing in quarantine at the Durango Hatchery? “Really well,” White says. It’ll be years before their offspring are released back into the wild, as it takes time for the river to recover from the debris pollution and the shoreline ecosystem to bounce back from the burn. “We’re taking steps to manage the best we can with the new reality. … So far we’ve been successful; the fish look good.”