Monday October 13, 2025
The Colorado Sun —
SHADOW MOUNTAIN LAKE — The mountain views from the crisp blue water — of subalpine fir shot through with canary-yellow aspen below the sugar-dusted Continental Divide — are sublime. In still coves, all is mirrored perfection. In breeze-rippled open water, waves play an angler’s tune against an aluminum hull.
And a storied river runs through it.
But Shadow Mountain Lake is less a pristine pool at the foot of wilderness than it is a manipulated fish bowl for the experimental gods of aquatic science.
As biologist Jon Ewert stands on the dock on a misty late September afternoon, impressive specimens of the brown trout anglers vie to pull from Shadow Mountain keep roiling the surface. Ewert’s thousand-yard stare is not for them.
“When I look at this lake, in my mind’s eye, all I see is a living carpet of white suckers,” said Ewert, a Colorado Parks and Wildlife aquatics manager. Ewert’s biology-based pitch papers to the bosses can extinguish, revive or introduce entire species in the biggest, most popular recreation pools of Grand and Summit counties.
In recent years, the state has dumped millions of fingerlings of brown and rainbow trout, cutbow hybrids and kokanee salmon into Shadow Mountain to promote an angler-friendly fishery in the shallow pool that connects natural Grand Lake to the much larger Lake Granby reservoir on the Colorado River.
At many other high-elevation Colorado reservoirs, trout and salmon thrive. Here at Shadow Mountain, “they stall out,” in Ewert’s studied assessment. They never get much past 12 inches.
The white suckers are eating their lunch. Quite literally.
White suckers aren’t meant to be here. The gods intended them to hoover decayed plants and bugs off the floor of lakes in the Midwest only. But the white suckers arrived in countless minnow buckets on fishing road trips of the 1950s, after the dam gates of Shadow Mountain first closed and backed up a relatively shallow 12-foot-deep pool bordering the western edge of Rocky Mountain National Park.
At the end of a Colorado bluebird day, minnow buckets got dumped overboard. White sucker minnows thrived on the aquatic plants lining Shadow Mountain’s littoral zone, the sun-penetrated waters near the shore. A deep Colorado reservoir may have some suckers surviving in a bathtub ring of the first 12 feet of vegetated shallows, but the colder, darker depths promote growth of trophy-size trout and salmon.
At Shadow Mountain, though, the white suckers reign supreme across the entire pond. Ewert’s regular netting tests find the homely sucker at 72% of the fish in the reservoir. As for a white sucker’s taste, let’s just say that even when renamed “mullet,” the fish is rarely preceded by the phrase, “Chef has prepared for you …”
In 2022, Ewert flexed his state biologist muscle to propose wholesale upheaval for the Shadow Mountain fish bowl.
Consider the tiger muskie.
In Minnesota and Wisconsin, lake-fishing anglers quest daily for 40-pound muskie as the ultimate basement-bar trophy. Northern pike, meanwhile, put up a great fight for their size but have voracious appetites that can quickly overwhelm any lake where they are relocated. Fertilize muskellunge eggs with northern pike milt in a hatchery, and you get a genetically refined fighting machine called the tiger muskie.
Which is also sterile. Meaning, it will die of old age after 15 years of harassing white suckers, and not reproduce along the way.
You swallow the bird to catch the spider to capture the fly …
Shadow Mountain could become a rare tiger muskie magnet in Colorado, drawing from far and wide a new set of high-spending anglers on top of the healthy brown and rainbow trout economies of nearby lakes and rivers. Fishing is the second-largest source of outside revenue for Grand County, Ewert notes, after Winter Park’s cascade of skiing dollars.
So tanker trucks backed up to Shadow Mountain’s boat ramps in spring of 2023 and dumped 13,000 tiger muskies under strict orders to maul the local mullet. It’s the largest such population-change experiment in recent CPW history, with Ewert convincing his bosses to commandeer the entire tiger muskie stock from all state hatcheries that year.
There were a few grumbles over the plan from Grand County residents who don’t want to see brown trout hounded out of Shadow Mountain, said Trail Ridge Marina employee Kris Holinka, helping pull private boats out of the water at Shadow Mountain’s ramp.
“But most of the response is very positive, and people are really excited, and surprised,” Holinka said. Her boat-pulling partner, James Newberry, pulls out his phone and displays a photo of a happy customer showing off a recent tiger muskie catch at the marina dock.
“They’re surprised at how big they are,” Newberry said. “It sounds like it could become a destination fishery. And people I’m talking to on the docks are saying that they’re excited about that.”
To give the lake’s transformation a chance, Ewert had to simultaneously trim the Shadow Mountain menu. If the state kept dumping 100,000 tasty rainbow snacks a year, the tiger muskies would never order anything else.
“A 10-inch hatchery-produced trout coming off of a truck is the most naive fish imaginable in terms of predator avoidance,” Ewert said. “And they’re also pretty high in caloric content.”
Translation: The rainbows may be stupid, but the tiger muskies — comparatively — are not.
Cut off the state-sponsored, five-star cuisine, and the white suckers would begin to disappear.
“If you force them to, if you give them the choice of either starve to death or make your living off of suckers, they’re going to make their living off of suckers,” Ewert said.
Shadow Mountain is the only Colorado reservoir where the state has completely benched all the veteran trout players in favor of a new tiger muskie quarterback.
What could possibly go wrong?
The truism in wildlife management is that one person’s introduced predator is another person’s invasive species.
“I mean, the whole history of fisheries management in North America, more than 100 years of it, is just wave after wave after wave of unintended consequences,” Ewert nods. He keeps one eye on Shadow Mountain’s remaining brown trout roiling the water near the return-canal inlet, bringing water back from Lake Granby to distribute to the Front Range through the Adams Tunnel.
Easterners brought the tamarisk plant west for decoration and riverbank-shoring, and decades later the “salt cedar” chokes Western river channels and drinks up valuable water. Chicago River engineers electrified the inlet to Lake Michigan in hope of keeping the voracious Asian carp out of the Great Lakes. Zebra mussels rode in the bilge of trading ships from Ukraine and have now landed in the Colorado River, terrorizing Colorado Parks and Wildlife biologists now trying everything to stop them.
Then again, nearly all the Colorado lakes the biologists are playing with are themselves an invasive construct. Water now flows and pools where only sagebrush and the rare cottonwood were meant to bear witness to the arid climate.
“These reservoirs, Shadow Mountain included, across the Intermountain West, by their very nature, are artificial fisheries,” Trout Unlimited Upper Colorado River project manager Stephen Klobucar said. Managing fisheries for the good of both anglers and coexisting local wildlife is a good modern development in the hands of careful, experienced researchers like Ewert, Klobucar said.
“I think John’s probably one of the premier biologists in the state that I would trust to manage this system accordingly,” Klobucar said.
One difference in the modern era, Ewert said, is the ongoing lab and hatchery research that searches for sterile hybrids in many species as a potential control measure in the wild.
When the released species can’t reproduce, Ewert said, “it doesn’t have to be a permanent decision.”
Shadow Mountain is not Ewert’s first fish wrangling, not by a long shot. He mentions trying to establish arctic char — a salmon species familiar from the Yukon to Svalbard — as an exciting addition to Lake Dillon. After a CPW refresh as recently as 2015, the in-demand char are now self-sustaining and the only viable group in reservoir in the Lower 48 states.
That said, there are far more safeguards to species introduction in Colorado than just asking for a receipt at the local pet store. Not only do Ewert’s proposal papers have to be vetted by his biologist colleagues and his Department of Natural Resources bosses, anything happening in the all-important Colorado River Basin watershed must also get the nod from state biologists from Utah to California. No local project should threaten to unleash invaders or predators downstream in the basin that serves 40 million people in seven states.
Tiger muskie hybrids occur in nature where muskies and northern pike inhabit the same Midwestern fisheries, but science has made hatchery-bred hybrids more successful and cheaper decade after decade. Wildlife managers also have decades of experience now observing the fates of host and introduced species alike over time after the nonreproducing tiger muskie arrives.
Tiger muskies that escape the Shadow Mountain experiment — and they already have — may eat up some of the desirable trout species down river in Lake Granby or the Colorado River channel toward Kremmling. But they will be lone rangers and won’t live more than a few years.
“Every lake spills fish,” Ewert said. “We don’t believe it’s happening in what we call ‘biologically significant’ numbers.”
So far, so good
When Ewert squints like Ahab at the Shadow Mountain surface and imagines nothing but the dreaded white sucker lying in wait below, how does he know what’s really happening down there?
When the 13,000 small tiger muskies were first added to the lake in June 2023, biologists concentrated the releases at shady shore overhangs and island coves to give the youngsters some cover. Annual fish surveys, though, spread 20 gill nets for six hours each into every nook and cranny of the lake, from those overhangs to algae-plastered banks in sun-blasted shallows.
So far, so good
When Ewert squints like Ahab at the Shadow Mountain surface and imagines nothing but the dreaded white sucker lying in wait below, how does he know what’s really happening down there?
When the 13,000 small tiger muskies were first added to the lake in June 2023, biologists concentrated the releases at shady shore overhangs and island coves to give the youngsters some cover. Annual fish surveys, though, spread 20 gill nets for six hours each into every nook and cranny of the lake, from those overhangs to algae-plastered banks in sun-blasted shallows.