A Species in Time
Cutthroat trout are the only trout species native to the Southern Rocky Mountains. Different subspecies and strains of cutthroat trout evolved through millions of years of geographic isolation. In Colorado, this has resulted in four distinct cutthroat trout subspecies as we understand them today: Rio Grande, Colorado River, Yellowfin (Arkansas River basin, extinct), and Greenback (South Platte River basin). Colorado Parks and Wildlife has a page focused on the state’s native cutthroat trout subspecies here.
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Photo courtesy of Tyler Kanaval.
Greenbacks (Oncorrhynchus clarkii stomias) prefer to live in clear, cold, well-oxygenated streams that have abundant pools and runs, clean gravel, and aquatic insects. They can also thrive in alpine lakes with cold, high-quality water and well-oxygenated spawning beds.
Size
Greenback size is variable based on the available habitat. In smaller headwater streams adults are generally 6-10 inches in length. In larger streams and rivers, as well as in lakes, adults can reach larger size, 14 inches or longer.
Diet
Greenbacks primarily feed on aquatic and terrestrial insects, but like other trout at larger sizes they can also eat smaller fish.
Color
Greenbacks display a variety of colorations, including bright crimson red in the lower jaw and throat that gives the cutthroat its name. They frequently have larger spots concentrated near the tail.
Spawning Season
Greenbacks spawn in the spring or early summer following runoff, when water temperatures approach 50 degrees.
Lifespan
Greenbacks typically live 5-8 years.
Native trout Subspecies & Lineages
There are six lineages within four subspecies of native trout that were once endemic to rivers in Colorado: The Yellowfin Cutthroat (Twin Lakes and Arkansas River Watershed), currently believed to be extinct; the Rio Grande Cutthroat in the San Luis Valley and New Mexico; the Greenback Cutthroat in the South Platte River Basin; and the Colorado River Cutthroat on the western slope comprised of 3 distinct lineages (San Juan, “Green” Gunnison/Colorado, and “Blue” White/Yampa). You can see their geographic ranges below.
