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CPW releases 108K tiny rainbow trout into Poudre River as restoration efforts continue after 2021 debris flow

Posted: 5:15 PM, Aug 23, 2023
Updated: 2023-11-08 10:23:29-05
rainbow fish babies for poudre river release aug 23 2021
Baby rainbow trout in the Poudre River

LARIMER COUNTY, Colo. — Bucket by bucket, thousands of tiny rainbow trout were released into the Poudre River on Wednesday morning, part of an ongoing effort to restore the fishery that was decimated by a massive debris flow in 2021.

Colorado Parks and Wildlife (CPW) worked alongside volunteers from Rocky Mountain Flycasters, the local Trout Unlimited Chapter, to introduce 108,000 little trout — no more than 2 inches in length — to their new habitat. Under scorched hillsides from the 2020 Cameron Peak Fire, they carried buckets of the fish from parked trucks to the waterway, and gently released the animals.

This is part of an endeavor that began in the fall of 2021 to rebuild the river's fishery following the 2020 wildfire and a subsequent debris flow about a year later.

The 2020 Cameron Peak Fire in Larimer and Jackson counties left much destruction in its wake once it was finally extinguished in early December 2020 after igniting on Aug. 13, 2020. In total, the fire had burned more than 208,000 acres, destroying more than 450 structures along the way. To date, it remains Colorado's largest wildfire in recorded history.

Cameron Peak Fire contained_Inciweb
This map shows the final burn area of the Cameron Peak Fire, which scorched more than 208,000 acres. The Poudre River follows Highway 14 through the burn scar.

According to the Coalition for the Poudre River Watershed, nearly 600 miles of the Poudre watershed, including the Cache la Poudre River (typically shortened to the Poudre River), were within the burn perimeter.

A brief introduction to the waterway: The Poudre River is Colorado's only nationally designated Wild and Scenic River, according to the U.S. Forest Service. Much of the river follows Highway 14 in Larimer County. It's often used for not only its views, but camping, rafting, hiking, mountain biking and fishing. Cutthroat trout and introduced brown and rainbow trout are typically plentiful in the river, USFS said.

In the Cameron Peak Fire's immediate aftermath, the fisheries and aquatic wildlife was, generally speaking, OK even though the landscape was severely damaged, said CPW Aquatic Biologist Kyle Battige.

But by the spring and summer after the Cameron Peak Fire, when heavy rains moved in, the Poudre River and its tributaries suffered from soot, ash, charred debris and more flowing into the waterways. Flash flooding was prevalent in July 2021 — the Black Hollow Debris Flow's flooding and mudslides on July 20 killed four people and decimated the Poudre River fish population.

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Battige said the river was black and "just choked with sediment," which prevented fish's ability to exchange oxygen across their gills and they suffocated.

He was one of the few people with CPW who ventured out to the Poudre River the day after the debris flow to evaluate the damage. He said dead fish littered the bank.

“Being out here the day after that Black Hollow slide was pretty shocking," he said. "You looked at the river and you knew it was pretty bad. And then to see the magnitude of loss to the fishery and the resource — it was significant.”

Aquatic biologist Kyle Battige dead poudre river fish
Aquatic biologist Kyle Battige holds up dead trout pulled from the bank of the Cache la Poudre River on July 21, 2021, the day following the flash flood and debris flow on the river.

Aquatic biologists and technicians installed stations to monitor impacts to aquatic resources along the Poudre and found that the stations downstream of the Black Hollow Creek confluence saw "dramatic impacts" to the fish populations, CPW said.

“No fish, outside of a single brown trout that had migrated downstream between the dates of the debris flow event and sampling event, were captured during sampling within stations from one to 16 miles downstream of Black Hollow Creek confluence, suggesting a complete loss of the fishery within that reach,” Battige said in 2022. “It was not until the Stove Prairie station, 20 miles downstream, that trout were captured."

The negative impacts were measured more than 40 miles downstream at Lyons Park.

When compared to historic estimates, a CPW survey found that trout numbers fell up to 80% in sections of the Poudre River after the floods and mudslides that summer.

poudre river trout impacts_comparing to 2021
This graph shows trout population estimates, with the blue bars showing historic estimates and orange bars showing 2021 estimates. The vertical black dashed line represents the Black Hollow Creek confluence. Note the substantial decrease from historic to 2021 estimates with no fish being captured downstream of Black Hollow until Stove Prairie Road. From Stove Prairie Road, downstream numbers were reduced until Lee Martinez Park, 46 river miles downstream.

Beginning in the fall of 2021, CPW started to rebuild the fishery, acknowledging that the process will take possibly decades to complete.

"The management plan is to stock whirling-disease resistant strains of rainbow trout in an attempt to establish their populations prior to brown trout naturally migrating back to these impacted reaches and increasing in abundance," CPW said in June 2022. "The goal will be to build currently impacted reaches that are void of fish into rainbow trout strongholds and have the reaches that were not at all impacted or less impacted remain brown trout dominated reaches, thus providing more diverse fishing opportunities."

Nature started its own recovery efforts too: Microbes and insects in the water began their work as natural cleaning agents and the water that returned to the Poudre watershed has been cool, which helps keep temperatures low and benefits the fish, according to research at Colorado State University.

Cameron Peak Fire_Aug 23 2023 view
Scorched trees above the Poudre River as seen on Aug. 23, 2023.

On Wednesday, for the second year, CPW and the Trout Unlimited Chapter volunteers introduced 108,000 rainbow trout, all between 1 and 2 inches long, to the Poudre River. Battige explained that they stock a lot of small fish because their overall survival rate is generally lower than an adult fish.

"We’re really focusing on whirling disease-resistant rainbow trout in this core 20 miles of reach that was most impacted," Battige said.

This effort will continue for several more summers. Each subsequent fall, CPW will return to evaluate the work and determine if they need to make any adjustments for the following summer's fish release. The Coalition for the Poudre River Watershed said a fire-affected watershed may need a decade to recover hydrologically from a blaze.

“This is an important endeavor today because the fisheries are important, both in terms of the overall health of the ecosystem, of the Poudre River — fish are important to that — and from CPW’s standpoint in terms of our mission. That aspect is important as well as providing recreational opportunities and angling," Battige said.

rainbow fish babies for poudre river release aug 23 2021
More than 100,000 tiny rainbow trout were released into the Poudre River on Aug. 23, 2023.

Local communities rely heavily on recreation and fishing in the Poudre Canyon, and nearly two dozen volunteers wanted to help CPW because they are also passionate about the fishery and river, he said. Releasing more than 100,000 fish in a day would be a difficult task for CPW alone.

Frank Reid, one of the volunteers, said protecting the Poudre watershed is very important to him. He fishes there often, and is a member of Rocky Mountain Flycasters. He said the river has made a remarkable recovery since 2021.

Frank Reid fisherman
Frank Reid helped CPW with a large release of small rainbow trout into the Poudre River in August 2023.

“It was catastrophic," he remembered of 2021. "It was brutal and I happened to drive past the Black Hollow where the water came down into the Poudre and started the destruction downstream, and the power of that water was astonishing. The size of the boulders and the debris that came down was just massive and very impressive. I could understand how it destroyed so much fishery downstream.”

He worked with CPW for the rainbow trout release in 2022 as well, and said it was a fun and well-coordinated day. People enjoyed the work, he said.

Reid also encouraged others to take time to protect the outdoor spaces they love.

"If you're not a fisher person, if you like to hike or whatever you want to do in the outdoors, there are ample opportunities to volunteer to help protect the areas that you enjoy the most," he said. "Take initiative and look for ways and organizations that are doing work that you like to help you do what you like, and you'll find opportunities just like I did."

CPW releases 108K tiny rainbow trout into Poudre River as restoration efforts continue after 2021 debris flow

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