It took 150 years or so, but the story of the greenback cutthroat trout finally rose to the surface. Released Sept. 24, research by Jessica Lynne Metcalf and a team at the University of Colorado at Boulder has shredded the scientific community's assumptions about the journey of the cutthroat in modern times, while likely revolutionizing conservation efforts for all sorts of endangered species.
Before the study, Colorado was thought home to four subspecies of cutthroat: the yellowfin, extinct since approximately 1903; the greenback, surviving in a few mountain streams; the Colorado River, spread across the state; and the Rio Grande, which swam only in the Rio Grande basin. It was assumed that most of the fish still inhabited waters at least close to their native range. The greenback, for instance, was thought to be native to both the Arkansas River Basin and the South Platte. It was initially thought Bear Creek's fish were natives.
What the study found, however, was that Colorado once had six subspecies of cutthroat. In addition to the known variety, an extinct subspecies had once swam the San Juan drainage, and the Colorado River cutthroat is actually two subspecies.
What's more, of the living subspecies only the Rio Grande swam in its native habitat. The rest were driven out by man-made pressures; competition from nonnative fish; and people who scattered them elsewhere.
Between 1885 and 1953, more than 750 million rainbow, brook and cutthroat trout were "stocked" in Colorado, most by government workers. The greenback, it turned out, was native only to the South Platte. Bear Creek was actually once fishless, but was stocked with greenbacks by a homesteader in 1882.
But the most surprising discovery was just how rare the greenback truly was — confined to Bear Creek. No reservoir feeds the creek, which reduced the likelihood that competing fish would be stocked, and the bottom of the creek is blocked by old Colorado Springs Utilities infrastructure.
"Ironically," the study notes, "while stocking contributed to the decline of native cutthroat trout throughout their range ... it appears to have also inadvertently prevented the extinction of this unique lineage."
Metcalf's study, initiated by the Greenback Cutthroat Trout Recovery Team in June 2009, was groundbreaking not just for its findings, but for its methods. Records proved that most stocking in Colorado took place between 1885 and the early 20th century, meaning that most fish were still in their natural habitat 130 years ago. Using that information, Metcalf secured fish samples, preserved in ethanol, from museums and academies across the nation. All samples dated to between 1857 and 1889.
DNA was carefully extracted from the ancient samples and compared to modern fish DNA. Such old samples being used in testing was a scientific breakthrough — impossible just a few years ago — that could steer the path of conservation in the future.
"With specimens collected up to 150 years ago, our study pushes back the age for recovering DNA from ethanol-preserved specimens for population-level studies by over two-fold and demonstrates the feasibility of molecular mining of archived samples," the study notes. "Establishing the timing of human disturbance, coupled with the use of ancient DNA techniques for retrieving phylogenetic information from predisturbance historical samples, paves the way forward for developing conservation goals aimed at restoring threatened and endangered species to their native ranges."
Leith Edgar, spokesperson for the U.S. Fish and Wildlife Service, says the findings go to show that "the moment we think we have nature figured out, science proves otherwise."
"We look at this [study] as evidence that science is ever-evolving, and we need to be open to the fact that what we know today isn't always going to be the same as what we figure out down the road," he says. "Being aware of that evolution in science and keeping an eye open for it certainly is going to benefit all manner of species."