Category: Nature & Science

Greenback Trout was Once Considered Extinct

DENVER – After more than a decade of intensive efforts to rescue the greenback cutthroat trout from the brink of extinction, Colorado Parks and Wildlife announced Friday it has discovered that the state fish is naturally reproducing in Herman Gulch, one of the first places the agency stocked it in its native South Platte River drainage.

This is a huge breakthrough by CPW’s aquatics team considering that in 1937 the greenback cutthroat trout was considered extinct. For decades, it was believed only two native cutthroat – the Colorado River and Rio Grande – had survived while the greenback and yellowfin had succumbed to pollution from mining, pressure from fishing and competition from other trout species.

In 2012, CPW confirmed that tiny Bear Creek, on the southwest edge of Colorado Springs and in the Arkansas River drainage, was home to an unlikely population of wild greenback cutthroat trout. Outside their native range, the fish are believed to have been brought to Bear Creek from the South Platte Basin in the late 1800s for a tourist fishing enterprise.

The discovery triggered a massive effort by CPW and the Greenback Recovery Team – a multi-agency group of state and federal aquatic researchers and biologists – to protect the 3½-mile stretch of water holding the only known population of naturally reproducing greenbacks.

After a decade of work to protect and reproduce greenbacks, the Herman Gulch discovery marks a major milestone.

“While we will continue to stock greenback trout from our hatcheries, the fact that they are now successfully reproducing in the wild is exciting for the future of this species. This is a huge wildlife conservation success story and a testament to the world-class wildlife agency Coloradans have in Colorado Parks and Wildlife. Colorado’s ecological diversity strengthens our community, supports our anglers, and our thriving outdoor recreation economy,” said Gov. Jared Polis. “CPW’s staff and our partner agencies have worked for more than a decade to restore this beloved state fish, and today’s news truly highlights the success of the work.

The governor’s thoughts were echoed by officials throughout CPW.

“The bedrock mission of Colorado Parks and Wildlife is to perpetuate the wildlife resources of the state,” said CPW Acting Director Heather Dugan. “This is a tremendous example of CPW fulfilling its mission. I am so proud of all the aquatic researchers, biologists, hatchery staff, volunteers and partner agencies who helped achieve this milestone of naturally reproducing greenback cutthroat trout.

“Despite more than a decade of setbacks and frustrations, CPW staff worked as a team across departments and across regions, stayed focused on the goal and now we gave this great news. It’s a great day.”

Front-line aquatic researchers and biologists celebrated the news.

“It’s just great to see all the hard work everyone has put in to save these fish is starting to pay dividends,” said Kevin Rogers, CPW aquatics researcher who has devoted much of his career to rescuing the greenbacks. “This is just another affirmation that our conservation practices work and that we can save species on the brink.”

In the years since the 2012 confirmation of greenbacks in Bear Creek, CPW has worked with its partners including U.S. Forest Service to protect and improve the creek habitat and the surrounding watershed and to develop a brood stock –  a small population of fish kept in optimal conditions in a hatchery to maximize breeding and provide a source of fish for the establishment of new populations in suitable habitats.

Each spring, CPW aquatic biologists have strapped on heavy electro-fishing backpacks to painstakingly hike up Bear Creek to catch greenbacks and collect milt and roe – sperm and eggs.

Then, they use the milt to fertilize all the roe in a makeshift lab on the banks of the creek. All the spare greenback milt collected is then raced to the Leadville National Fish Hatchery to fertilize eggs from the greenbacks in its brood stock. In 2014, an additional broodstock was started in Zimmerman Lake, near the headwaters of the Cache la Poudre River and thus within the greenback’s native South Platte basin.

All fertilized eggs are then sent to the CPW Mount Shavano Hatchery in Salida where they are kept in a greenback isolation unit where conditions are carefully controlled to allow the maximum number of eggs possible to hatch.

In 2016, CPW began stocking the greenback fry that hatch from those eggs into Herman Gulch west of Denver. Stocking into other streams in the South Platte drainage soon followed. Today, fledgling greenback populations exist in four South Platte basin streams. But only the fish in Herman Gulch have existed long enough to reach adulthood and begin reproducing.

CPW and its partner agencies in the Greenback Recovery Team and others including Trout Unlimited have carried bags of greenback fry miles up steep mountain trails every summer since trying to get them into water where they might reproduce. The agency tried different age classes and sizes each year over a three-year period.

“The news of the natural reproduction of greenback cutthroat trout in Herman Gulch is truly monumental,” said Josh Nehring, CPW’s assistant aquatic section manager who previously was senior aquatic biologist in the Southeast Region and oversaw efforts to protect the lone greenback population in Bear Creek.

“CPW aquatic biologists in the Southeast Region have worked incredibly hard to protect and preserve the only known population of greenbacks in Bear Creek,” Nehring said. “Our hatchery staff along with our federal hatchery partners overcame immense obstacles to be able to replicate the species in captivity. Now to see them on the landscape in their native habitat replicating on their own is a huge sense of accomplishment for everyone involved.”

The news of reproducing greenbacks in Herman Gulch was never a sure bet. And over the years CPW aquatic biologists even feared they could lose the population in Bear Creek. There was intense pressure from increased recreation on adjacent trails and traffic on a road that parallels the creek, delivering sediment into Bear Creek.

There were flash floods that could have wiped out the rare trout. Invasive and aggressive brook trout remain a constant threat to move upstream and outcompete the greenbacks. And there have even been wildfires that have erupted in the forests that surround the creek.

Worst was a survey conducted by CPW aquatic biologist Cory Noble in the fall of 2020 that showed a troubling decline in the greenback population in Bear Creek with no reproduction that year. Noble launched even greater efforts to modify the habitat to reduce the influx of sediment, to patrol for invasive brook trout and to monitor the population by less stressful techniques using underwater cameras.

While Noble worked on Bear Creek, a long list of his CPW aquatic colleagues were spending countless hours and piling up miles hiking high-country streams in the gritty work of identifying host creeks, preparing them for greenbacks and then hauling them miles in heavy backpacks to be stocked.

“As our colleagues worked to protect the Bear Creek population and successfully raise them in our hatchery, our Northeast Region biologists were on the ground building a wild brood source at Zimmerman Lake and searching for just the right habitats where we could remove non-natives, safely stock the greenback and protect them from other threats and give them the best chance to survive and reproduce,” said Jeff Spohn, senior aquatic biologist in the Northeast Region.

Leading that effort was Boyd Wright, aquatic biologist in Fort Collins, who has dedicated the past decade to returning wild populations of greenbacks to their native range in the South Platte Basin.

Like Noble on Bear Creek, Wright and his team hauled heavy electro-fishing backpacks up Herman Gulch and the other stocking sites to study the fish they had stocked. After some disappointments, just a few days ago they made a stunning discovery: they documented greenbacks up to 12 inches long and found fry.

“Our team of field technicians literally high-fived right there in the stream when we captured that first fry that was spawned this year,” Wright said. “When moments later we captured a one year old fish produced in 2021, we were truly beside ourselves.”

“After many years of hard work and dedication, it is extremely satisfying to see our efforts paying off.”

It’s news the entire agency had waited to hear for a long time: greenback cutthroat trout that were naturally reproducing in Herman Gulch.

“This is a great achievement for the recovery of greenback cutthroat trout,” said Noble, the Colorado Springs-based aquatic biologist who has shouldered daily responsibility for the greenbacks in Bear Creek. “It is really rewarding to see that all of CPW’s hard work is paying off.”

Similar relief was voiced by Bryan Johnson, hatchery manager at Mount Shavano Fish Hatchery in Salida. Johnson, a 20-year CPW hatchery veteran, has endured 10 years of frustration trying to find the right combination of water temperatures and genetic combinations just to get greenbacks to survive in the hatchery, much less in the wild.

“This represents a lot of years and a lot of hard work and a lot of disappointment along the way,” Johnson said. “Frankly, we have low survival rates in the hatchery compared with other strains of cutthroat. We started the broodstock in 2008 and here it is 2022 and we’re finally seeing the first natural reproduction. We’ve gone through a lot to get these fish back on the landscape.”

Just this week, Johnson and staff were bagging greenback fry at 4:30 a.m. so he could drive them 11 hours up gravel roads to a new reintroduction site. There, he handed off the fish to the Northeast Region team led by Kyle Battige, aquatic biologist from Fort Collins.

“This is just the start,” Johnson cautioned. “We need more. We’ve only got a few places where we have greenbacks  on the landscape. But it’s awesome to see natural reproduction in Herman Gulch.”

Harry Crockett, CPW’s native aquatic species coordinator and chair of the Greenback Recovery Team, said he’s confident the news of natural reproduction in Herman Gulch will be followed by even better headlines.

“We found a greenback that was born in Herman Gulch that was already a year old,” Crockett said. “This indicates successful reproduction both this year and last, plus overwinter survival. This is important because trout that survive to one year are likely to live even longer.

“And with more of these reintroductions going, we expect to find more reproduction in more places in the coming years.”