Those who make their way to Colorado’s abundant trout streams, high-country lakes and sweeping rivers for a day of fishing probably think they have it pretty good. The scenery is generally inviting, and the fish are often biting.

But as it turns out, things could be a whole lot better. In fact, say leaders of the cold-water conservation group Trout Unlimited, they should be.

“There’s no upbeat way to read this. This is grim,” TU president and CEO Chris Wood said as his organization released its first-ever comprehensive ” State of the Trout” report Tuesday. “Native trout in the United States are in big trouble. Of the 28 species that historically occurred in our waters, three have already become extinct. More than half of those that remain occupy less than a quarter of their historic habitat. To see it so starkly laid out, that’s tough medicine.”

The report, authored by TU senior scientist Jack Williams, examines both old and new threats facing our nation’s cold-water fish, and the impact those threats are having today on native trout populations.

When it comes to such threats and impacts, the report notes, Colorado finds itself squarely in the bull’s-eye.

Already Colorado must accept responsibility for one of the two extinct subspecies of cutthroat trout. Yellowfin cutthroat once native to the state have long since disappeared. What’s more, genetically pure greenback cutthroat trout currently occupy less than 1 percent of their native range — limited to just four miles of stream and a single lake — and are listed as threatened under the federal Endangered Species Act and a species of special concern by state agencies.

Two other species of cutthroat trout native to the state — Colorado River cutthroats and Rio Grande cutthroats — occupy only about 10 percent of their respective historical habitat and fall into the “special concern” and federally recognized “sensitive species” categories as well.

Perhaps the most difficult pill for Colorado anglers to swallow, though, is the reality that those specific breeds of cutthroat truly are the only trout that belong in the cold waters of Colorado. All those plump rainbows, feisty browns and beautiful brook trout fishermen have been reeling in through the years are a significant part of the problem, the report says.

“Habitat loss is clearly the No. 1 threat, but right behind it are the impacts of climate change and non-native species,” Wood said. “It’s imperative that we become more selective and a bit smarter about where we stock non-native fish, especially when it comes to stocking non-native fish on top of native fish. State agencies may need to take a look at their practices and tweak or change them in order to give more bias to native fish.”

So are Colorado’s trout worse off than they were, say, a century ago? The answer is a definite maybe.

The introduction of non-native rainbow, brown and brook trout has been both a blessing and a curse. Generally speaking, the fish have thrived and established great sport fishing opportunities around Colorado, contributing greatly to the economy and wildlife management coffers while enhancing a culture of outdoor awareness.

But imported brown trout, for example, are so successful in occupying new habitats that they now threaten remaining native trout populations, Williams wrote. Hatchery-produced trout are often highly domesticated and maintain poor survival abilities compared with native trout, yet repeated stockings can swamp out native populations.

“The fact is that angling provides access for people to become conservationists, so our view is that in certain systems there’s been so much change, they’re so off from what they were historically, it’s best to manage them as the great wild fisheries they’ve become,” Wood said. “It’s TU’s belief that we can provide the most opportunity for the most anglers by managing quality habitat. But it’s incumbent upon us who care about wild fish to take special care to keep native fisheries in tact.”