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The countdown began with 19 first graders plopped on their bellies, gazing off the edge of a small pier into the dark waters of Berkeley Lake in northwest Denver. Sporting waders and standing knee-deep in the shallows, teacher Michelle Morton passed before them holding a plastic container.

Inside, a tank-raised fingerling rainbow trout shimmered in the midday sun, about to embark on its return to a natural environment. “Three … two … one …” the kids chanted, as Morton and a student helper dipped the container into the lake. A cheer rose as the tiny fish wriggled into its new habitat. 

In a sense, the countdown began last fall, when K-5 science classes at Centennial Elementary School, just a strong fly rod cast from the lake, arrived at Morton’s room to find 200 fertilized eggs in a 55-gallon tank equipped with a bubbler, a chiller and an automatic feeding mechanism. That signaled the start of Trout in the Classroom, a monthslong education customized for each grade level and replicated in schools across the state, with the help of state and local chapters of the conservation group Trout Unlimited.

Since October, the kids have charted the trout’s growth — and in some cases, their deaths. Morton recounted “an exciting day” in January when one of the bigger fish ate a smaller one, whose chomped tail fin dangled from the larger fish’s mouth for hours. The third graders noticed the big event, which they found at once fascinating and disturbing.

It led to interesting conversations about animal life cycles and survival.

“I’ve been talking about the release for a while, and now that it’s happening today, some of the kids are really excited and some of them are sad,” Morton said. “It’s really been fascinating to hear their questions about what happens next.”

Centennial Elementary School students watch as teachers transfer a trout to be released into Berkeley Lake on May 6 in Denver. (Photos by Hugh Carey, The Colorado Sun)
A fingerling rainbow trout before its release into Berkeley Lake.
First grader Emma Bornstein cheers after releasing a trout.

First graders Koen Parsell and Ella Jones, both age 6 and part of the first Centennial class to release their trout into the lake, paused afterward to reflect on a bittersweet goodbye.

“I wonder how he’ll survive in such a big lake,” Koen said.

“I’m happy he gets a new life,” Ella added. And then, after a pause: “Do they get tooken from their parents?”

Other kids wondered and worried how the young fish would elude predators, until a Trout Unlimited expert explained that they were hard-wired for survival — hence their instinct to immediately disappear into the shadows beneath the pier. 

A trout to be released into Berkeley Lake. (Hugh Carey, The Colorado Sun)

“I’m happy he gets a new life. … Do they get tooken from their parents?”

Ella Jones, 6

By the end of the day, every Centennial class had taken a front row seat to witness — like other schools before and after — the introduction of a 3- or 4-inch rainbow to Berkeley Lake. What they didn’t know was the story that had unfolded behind the scenes to ensure there would be enough fingerlings to go around.

Not just any fish can be released into the state’s waterways. State regulations require that a precise number of fish from any hatchery — and the school tanks fall under this rule — must be tested for a variety of pathogens in order to legally be released into Colorado waters. That means killing fish from those tanks and dissecting them. The smaller the fish population, the higher the higher percentage of trout that need to be sacrificed.

In order to guarantee enough trout for Denver-area classrooms to release, the Trout Unlimited folks — who supply the eggs and facilitate the releases — needed to figure out a way to maximize the yield from those hundreds of eggs.

To make certain that classes could get the most from the aquaculture, they first had to solve a math problem.

The Trout in the Classroom program is used by more than 5,000 classrooms in 35 states, with help from Trout Unlimited and other conservation-minded organizations across the country. The ethic behind the activity is simple: By nurturing the trout (or salmon, in some areas) from eggs to fingerlings, and then releasing them, students learn to connect the development of the fish with the quality of the water they’ll eventually inhabit.

Teachers can adapt the program to any age group and gather ideas from an ongoing library of lesson plans that might focus on something relatively simple, like life cycles, for younger students or something more complex, like water chemistry, at the high school level.

But the payoff for students lies largely in the release, which connects the final dots of their curriculum. And in Colorado, where the program has been underway for several years, the state’s unique testing to prevent the spread of pathogens — whirling disease spawned one cautionary tale — took a toll on the program.

I don’t like killing fish for any reason. And especially these poor buggers that have been raised in a tank. To kill ’em just felt wrong.

— John Davenport, Trout in the Classroom coordinator

Because the number of fish that survive from egg to fingerling in the classroom tanks often is relatively small, maybe less than a few dozen, the quantity available for release dwindled after testing — even though Colorado Parks & Wildlife, which oversees aquaculture in the state, required the Trout in the Classroom program to provide slightly fewer test fish. 

Because the school tanks generally use safer municipal water, the risk of disease transmission is lower, said April Kraft, senior fish pathologist for CPW’s Aquatic Animal Health Laboratory. Still, intentionally killing any of the fish — many of which students name as they develop distinguishing characteristics — revealed another downside of testing.

“Kids don’t want to see fish sacrificed,” Kraft said. “It’s heartbreaking. Unfortunately, they’re lethal tests. You can’t just draw blood like you can for a cow or horse.”

Centennial Elementary School teacher Michelle Morton, left, releases a young trout into Berkeley Lake with first grade students on May 6, 2022, in Denver. (Hugh Carey, The Colorado Sun)

It wasn’t just disturbing to the kids. John Davenport, Trout in the Classroom coordinator and former president of Denver Trout Unlimited, figured there had to be a better way that would ensure a more robust yield for the eventual release.

“What triggered the whole thing was I’m a catch-and-release angler,” Davenport said. “I don’t like killing fish for any reason. And especially these poor buggers that have been raised in a tank. To kill ’em just felt wrong.”

When an intern with the organization recoiled from the news that trout would be killed in order to perform the tests, she told Davenport, “that’s ridiculous.” He couldn’t disagree. So they started crunching numbers and figured out an alternative eventually dubbed the “nearly no-kill” release option.

The initial math looked something like this: According to state requirements, a tank of 50 trout would require 20 to be killed and tested for pathogens. For a tank of 100, 23 would need to be tested. For 500 fish swimming in the same tank, 26 would be sacrificed. 

Proportionally, the kill/test rate could range between 40% and about 5%, depending on the population of the tank. Add to that the natural attrition between egg and fingerling, and the math problem quickly swam into focus.

The rainbow trout, introduced to Colorado in the 1880’s into the Gunnison River, is identified by its side stripe and black spots. (Olivia Sun, The Colorado Sun via Report for America)

“Kids don’t want to see fish sacrificed.”

April Kraft, senior fish pathologist

Natalie Flowers, the youth education coordinator for Colorado Trout Unlimited, noted that one school with a low survival rate had only 29 fingerlings. They needed to test 20 in order to release nine. Davenport hatched an idea.

“The more I thought about it, the basic problem is these tanks aren’t big enough,” Davenport said. “Maybe we were approaching this in the wrong way.”

What if schools used the 55-gallon classroom tanks to raise the fish but then moved them to live for a specified period in a larger tank? The number required for testing would be proportionally smaller. Then healthy trout from the larger tanks could be distributed to classes for their release. 

The metro Denver classrooms gave it a try. They’ve begun consolidating their fingerlings in a few large tanks — one, at the Denver offices of the Greenway Foundation, a nonprofit that has been working since 1974 to reclaim the urban South Platte River, and two more located at Arvada West High School. From those tanks, relatively fewer trout have been culled and sent for testing to the U.S. Fish and Wildlife Service in Bozeman, Montana.

Once the tanks were certified safe, Denver Trout Unlimited volunteers transported fingerlings to schools across the Denver metro area for this spring’s release. 

The “nearly no-kill” protocol could really start to pay dividends next fall, after fish from smaller tanks have had a chance to mature in the larger tanks. A new timeline for the program will feature fall releases, followed by the delivery of new eggs, which the classrooms will nurture until it’s time for the fingerlings once again to be consolidated in the big tanks for testing over the summer.

And so the cycle continues.

Just a short walk from the Carson Nature Center in Littleton, 10 eighth graders from Options Middle School leaned into a gusting wind as they made their way to the bank of the South Platte River.

This was their moment, their opportunity to release 20 rainbow fingerlings into the river’s chilly current, which moved low and slow while bicyclists zipped by on the path behind them. They worked in a kind of relay, moving the fish provided by Denver Trout Unlimited from large buckets to smaller plastic trays and then, after stepping carefully down the rocky bank, to the clear shallows. Some of the fish headed straight for the deeper, safer water in the middle of the channel. 

Brittany Sanchez, 14, watched as her fingerlings disappeared to safety beneath a rocky ledge.

“They didn’t want to leave me!” she grinned.

“We hatched them from eggs,” 14-year-old Josh Merrill noted. “We learned to test the water, what temperature it has to be. I’m hoping these that we released will survive and maybe make a couple more generations of fish.”

Molly Goswick, eighth grader at Options Middle School, releases rainbow trout into the South Platte River on May 12 in Littleton. (Olivia Sun, The Colorado Sun via Report for America)

For older students, the TIC program offers exposure to a wider range of possibilities in STEM disciplines — science, technology, engineering and math. Davenport and Greenway Foundation founder Jeff Shoemaker used the COVID pause to experiment with the 100-gallon Greenway tank, employing telemetry and video to monitor tank conditions remotely — another tool to avoid massive loss due to temperature drops or changes in water quality. The tank doubled its previous yield.

Those technological improvements already are in place at the Arvada West tank and might eventually find their way to other schools to further enhance STEM options.

“Now,” Davenport said, “high school release day turns into career day.” 

Chris Madsen, a teacher at Arvada West High School, is in his second year of the program and has become an enthusiastic participant, as well as supervisor of the school’s larger tanks — an 85-gallon setup in his classroom as well as a 125-gallon tank in the school library. COVID protocols played havoc with student participation last year, but Madsen took care of the fish himself and kept his students updated on their progress. Last spring, he was able to get a field trip approved for a release into Clear Creek.

I wonder how he’ll survive in such a big lake.

— Koen Parsell, 6

He adapted the TIC program to include water quality management, which dovetails with students’ concurrent enrollment classes at Red Rocks Community College. He also worked with Davenport on tracking some of the fish after injecting them with a fluorescent polymer — a project he was hoping to replicate this spring before COVID derailed the plan.

“Trout release day last year was the most fun we had the entire year — and there weren’t a lot of fun days,” Madsen said. “They like the feeding and testing, it gives them a break during the school week. It’s as engaging of a thing as I’ve seen high school students doing. Tagging and release is some of the best workday learning they get.” 

Eighth graders from Options Middle School released 20 fingerling rainbow trout on May 12 into the South Platte River. (Photos by Olivia Sun, The Colorado Sun via Report for America)
The rainbow trout, introduced to Colorado in the 1880s into the Gunnison River, is identified by its side stripe and black spots.

When it comes to setting up a TIC program, Flowers, of Colorado Trout Unlimited, estimates start-up costs have run around $1,500 for equipment. Additional bells and whistles, like video and telemetry, could push the cost as high as $2,500. 

“That’s a lofty price for a school,” she allowed. “In the past, a lot have paid for it through fundraising and grants, or local Trout Unlimited chapters help fundraise or fully fund them. The good thing is, after the first year, costs go down dramatically.”

Options, the Littleton alternative school, has been using the TIC program for the last two years. Teacher Leah Crews’ classroom already had a tank and filters, so needed just a chiller — trout are a cold-water species — and eggs, which Denver Trout Unlimited provided. She said the school is considering a larger tank.

At Centennial Elementary in Denver, Morton literally immersed herself in the opportunities that culminated in the release into Berkeley Lake. She procured a grant to purchase her waders and large nets to aid in all sorts of science experiments. 

“I tell them Berkeley Lake is part of our school,” she said. “I want them to make that connection, to keep it healthy. It’s not just that it’s a fun place to go play, but our fish are gonna go there so we need to keep it healthy. Being able to release fish into the lake is just another connection for them of why we want to take care of a local waterway.”

And next fall, the countdown begins anew.

This story first appeared in Colorado Sunday, a premium magazine newsletter for members.

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Kevin Simpson is a co-founder of The Colorado Sun and a general assignment writer and editor. He also oversees the Sun’s literary feature, SunLit, and the site’s cartoonists. A St. Louis native and graduate of the University of Missouri’s...