A cutbow is a hybrid trout produced by the crossbreeding of a rainbow trout and a cutthroat trout. The name is a straightforward combination of its two parent species. Cutbows can occur naturally in rivers where both species share the same water, or they can result from deliberate hatchery breeding and stocking programs. They’re fertile, capable of reproducing with each other and with either parent species, which makes them both a popular sportfish and a source of conservation concern.
How Cutbows Form
Rainbow trout (Oncorhynchus mykiss) and cutthroat trout (Oncorhynchus clarkii) are closely related species that can successfully interbreed. In the northern Rocky Mountains, particularly in Idaho, Montana, Oregon, and Washington, these two species naturally share rivers and streams. Hybridization has been documented in pristine habitats that have rarely or never been stocked with hatchery fish, as well as in heavily stocked waters. So cutbows aren’t purely a human creation; nature produces them too.
That said, decades of intensive rainbow trout stocking across the American West have dramatically increased the rate of hybridization. When hatchery-raised rainbows are introduced into cutthroat habitat, the two species interbreed freely. Over as few as five generations of random mating, hybrid genetics can become thoroughly mixed into a population. In some streams, researchers have found that hybridization is heaviest near stocking sites and declines further downstream.
How to Identify a Cutbow
Cutbows generally look like rainbow trout with some cutthroat features mixed in. The most consistent giveaway is a faint reddish or orange slash under the jaw, the signature marking of cutthroat trout. On a pure cutthroat, this slash is bold and vivid. On a cutbow, it’s typically lighter and sometimes easy to miss.
Beyond the throat slash, coloration varies widely from fish to fish. Some cutbows lean heavily toward their rainbow parent, with a prominent pink lateral stripe and dense spotting across the body. Others show more cutthroat influence, with spots concentrated toward the tail and a lighter overall pattern. Pure cutthroat trout tend to have fewer, larger spots clustered near the tail, while pure rainbows are spotted more evenly across the body. A cutbow’s spotting pattern usually falls somewhere in between, which can make identification tricky without genetic testing.
Where Cutbows Live
Cutbows inhabit the same cold, clear streams and rivers that support their parent species. They’re found throughout the Rocky Mountain West, from Montana and Idaho south into Colorado, Wyoming, and parts of the Pacific Northwest. Like both parent species, cutbows are cold-water fish. Cutthroat trout are most commonly found where maximum daily water temperatures stay below about 20°C (68°F), though they can tolerate warmer water in some systems. Cutbows inherit similar temperature preferences, thriving in mountain streams, alpine lakes, and tailwaters below dams where cold water is released from reservoirs.
Their diet mirrors that of other stream-dwelling trout: aquatic insects like mayflies, caddisflies, and stoneflies make up the bulk of what they eat, supplemented by terrestrial insects that fall into the water, small crustaceans, and occasionally smaller fish. For anglers, this means cutbows respond well to the same flies and lures used for rainbows and cutthroats.
Fishing for Cutbows
Many anglers prize cutbows because they can combine desirable traits from both parents. Rainbows are known for aggressive feeding and acrobatic fights on the line. Cutthroats are often easier to fool with a fly and tend to inhabit beautiful, remote water. A cutbow can offer some of both: a willingness to strike that comes from its rainbow side and the stunning coloration inherited from its cutthroat parent.
Some state wildlife agencies intentionally stock cutbows in lakes and reservoirs. In these managed fisheries, cutbows can grow quickly and reach impressive sizes because they benefit from a phenomenon called “hybrid vigor,” where crossbred animals sometimes grow faster or larger than either parent species. In other waters, cutbows show up on their own wherever rainbow and cutthroat populations overlap. If you catch a trout that looks mostly like a rainbow but has a faint orange slash under its chin, you’ve likely got a cutbow.
Why Cutbows Concern Biologists
The same trait that makes cutbows interesting to anglers makes them a serious problem for conservation: they’re fertile. When cutbows breed with pure cutthroat trout, they dilute the genetic identity of native cutthroat populations. Over time, a stream that once held genetically distinct cutthroat trout can become dominated by hybrids, and the pure native fish effectively disappear. Biologists call this process “introgression,” and in many watersheds across the West, it’s already well advanced.
This is especially worrying for subspecies like the westslope cutthroat trout and the Yellowstone cutthroat trout, which have already lost significant portions of their historical range to habitat loss, climate change, and competition with nonnative species. Adding widespread hybridization on top of those pressures pushes some populations closer to the point where genetically pure fish no longer exist in a given watershed. Research in northern Rocky Mountain streams has shown that where stocking has occurred for decades, hybrid genetics become a permanent fixture of the population rather than a temporary blip.
Wildlife agencies in Montana, Idaho, and other states now manage this tension carefully. In some waters, they actively stock cutbows or rainbows for recreational fishing. In others, they work to protect remaining pure cutthroat populations by removing nonnative trout, installing barriers to prevent upstream migration, and monitoring genetic integrity over time. The challenge is balancing the recreational value of hybrid and nonnative trout against the biological need to preserve native species that took thousands of years to evolve.