There is a new – but ancient – branch on the cutthroat trout family tree, the San Juan cutthroat. Recently, Colorado Parks and Wildlife announced that biologists have discovered cutthroat trout in the San Juan River drainage that hold unique genetic traits, a bit different from other cutthroats found in Colorado.
This is welcome news for everyone who loves Colorado’s wildlife diversity. By finding and identifying this unique trout, Colorado Parks and Wildlife is helping to preserve an important piece of the natural heritage of Southwest Colorado – a cutthroat that we thought was extinct. It also shows the importance of ongoing scientific investigation as we’re still making discoveries in the 21st century!
But this discovery wasn’t accomplished overnight. The story of the San Juan lineage trout goes back more than 40 years.
I’m proud to have played a role in this find. As a young aquatic biologist in the late 1980s, I was encouraged to search for relict populations of cutthroat trout in the San Juan basin by my friend, colleague, and supervisor at the time, the late David Langlois. Thus began a decades-long quest for remnant populations of aboriginal cutthroat trout. Over the years, I was privileged to conduct this work with many dedicated field biologists and district wildlife managers while visiting some of Colorado’s most remote and beautiful places. Since 2006, Jim White, the current CPW aquatic biologist in Durango, has led the local cutthroat trout conservation effort.
In the 1970’s, the Colorado Division of Wildlife, as the agency was called then, began its transformation from a “fish and game” management emphasis toward the objective of preserving and protecting all wildlife species, including species in decline like native cutthroat trout.
Over the past 45 years, fish biologists and district wildlife managers with Colorado Parks and Wildlife have worked diligently to inventory existing trout waters statewide in order to identify and protect waters containing cutthroat trout. Within the San Juan River basin, extra effort was made to survey waters with no known history of fish stocking, with the objective of finding relict populations of cutthroat trout. This was a classic team effort. The U.S. Forest Service and private landowners proved indispensable in helping to identify the few pockets of cutthroat trout that still remain.
In the days before genetic testing, when we found isolated populations that were hanging by a thread and suspected that they might be a pure genetic strain, we worked to safeguard them. We made sure no other fish were stocked in those streams; we removed non-native trout; we built barriers to prevent non-native trout from migrating up into cutthroat trout habitat, and we even replicated one relict cutthroat population by moving some of its members to a nearby stream that previously held no trout but offered protection.
All along the way we were guided by the words of Aldo Leopold: “The first law of intelligent tinkering is to save all the parts.” In a very real sense, the fact that a San Juan lineage of cutthroat trout exists today is due to ongoing work of generations of biologists who believed in and followed Leopold’s conservation ethic.
And fortunately, one of those “parts” was preserved by naturalist Charles E. Aiken when he collected a couple of trout from the San Juan River near Pagosa Springs in the 1870s, preserved them and deposited them in the Smithsonian Museum. Those specimens were forgotten until 2012 when a team of researchers from the University of Colorado found them while doing research on cutthroat trout. The researchers clipped some material from the specimens for genetic analysis.
CPW’s Kevin Rogers, the agency’s cutthroat trout researcher, compared the genetic traits of the two historic specimens with DNA from cutthroat trout that existed in the eight small populations that biologists had preserved over the years. Much to everyone’s surprise, Rogers discovered the genetic characteristics of the existing populations very closely matched the trout specimens from 1874. The findings were confirmed last January and we were heartened to learn that we’d saved fish that we thought had gone extinct many years before.
The prevailing theory about the origin of today’s cutthroat trout subspecies is they descended from a common ancestor distantly related to Pacific salmon. During one or more interglacial periods, 3-5 million years ago, it is believed the ancestral cutthroat trout moved into the intermountain west from a flooded Columbia River basin. In this manner, ancestral cutthroat trout eventually became established in all of the major river basins of Colorado.
When the flood waters from the last ice age receded, the cutthroat trout found in each river basin were effectively isolated from cutthroat trout in neighboring river basins. During the intervening 2 million years, these trout developed local adaptations to their environment, and thus evolved into today’s multiple subspecies of cutthroat trout.
Applying modern genetic techniques in comparative studies of old museum specimens with today’s trout populations continues to yield unexpected surprises, and presents exciting opportunities in the world of conservation genetics.
For the San Juan cutthroat to survive in pure form after 140 years of non-native fish stocking in the region is a wonder in itself. Without question, these are some resilient fish. Most of the streams they presently inhabit are small, difficult to reach, nearly impossible to fish, and often overlooked. Some are found on private land without public access. However, they have also benefited in no small part from a helpful human hand.
While the outcome is far from certain, I am confident that Colorado Parks and Wildlife biologists and fish culturists have the knowledge, expertise, and commitment to bring back the San Juan cutthroat trout. They are building on a strong foundation that was laid over 40 years ago. Great things are possible when we remember to save all the parts.
While some may view the recent announcement of the rediscovery of the San Juan lineage of cutthroat trout as a curious wrinkle in the fabric of time, it is also a strong affirmation that fundamental principles of conservation biology, when carefully applied, may prevent ancient, native trout from disappearing from the face of the earth.
Mike Japhet is a retired senior fisheries biologist with Colorado Parks and Wildlife.
