Greenback/Chris Anderson
Although it’s been widely reported that biologists discovered a small population of greenback cutthroat in Utah’s La Sal Mountains, Trout contributor and scientist Dr. Robert Behnke disputes that these fish are actually greenbacks.
Read his argument, and weigh in on the debate in the comments.
Behnke writes:
The fall 2009 issue of Trout repeated the assertion that a population of greenback cutthroat trout was found in a stream on La Sal Mountain, Utah. This erroneous conclusion has been widely propagated in the media for the past six months. Genetic studies of Colorado River and greenback cutthroat trout have been ongoing for about 10 years. During this time wrong conclusions have often been made because natural genetic variation in both Colorado River cutthroat and greenback cutthroat led to incorrect assumptions due to inadequate sampling of small, fragmented populations. Sophisticated, state-of-the art technology was confused with “scientific proof.” In fact, the genetic studies show a flagrant violation of what science is all about.
Science is not about proof on certainty, but all about uncertainty—doubts that should be raised to challenge premature or wrong conclusions. The genetic studies are characterized by completely ignoring uncertainties. This resulted in a “type 1” error where something assumed to be true is, in reality, false. Previously, I have critiqued the genetic data, pointing out the dangers of premature and wrong conclusions. My column “Genetics: A Double-Edged Sword” appeared in the winter 2004 issue of Trout. Further discussion is found in my winter 2008 column, “Science and Endangered Species” as well as in the author’s notes following the greenback trout article in my 2007 book About Trout. My critique of genetic studies was repeated by John Randolph in the March 2008 issue of Fly Fisherman and by Ted Williams in the January-February 2008 issue of Fly Rod & Reel.
If anyone persists in claiming that the greenback occurs in Utah, I would point out an insurmountable uncertainty: How did they get there? In 1894, the only known introductions of greenback trout into the Colorado River basin occurred in the Gunnison and Roaring Fork rivers. It is highly doubtful that any of these greenbacks survived to reproduce during a period when nonnative rainbow trout were rapidly replacing native cutthroat. If they did, they would have had to maintain their purity during an incredible journey to La Sal Mountain. One might invoke stocking by aliens from outer space, which can’t be disproved.
By Bill March 22, 2010 - 3:13 pm
When this story first broke, my first thought was “I wonder what Behnke will have to say about this.”
A few months earlier , we had Dr. Behnke here in New Mexico to speak at a chapter banquet. I had a lengthy discussion with him about cutthroat migration and genetics, as this was not long after the famous paper doubting the genetic purity of Colorado River cutthroats used in restorations. It was clear that Behnke was on to something, and that stories like the La Sal greenbacks have more to say about our genetic mapping of these species than they do about the fantastic tales of fish crossing divides and swimming hundreds of miles with their genetic purity in tact. It’s time to re-think the science before we do something we regret.
By Dan March 29, 2010 - 9:03 pm
In talking with the regional fisheries biologist overseeing the potential greenback population in the La Sal mountains…the biologist indicated that in addition to the genetic testing being done (which only indicated a preliminary connection) the La Sal population has mirrored that of other greenback populations most recently discovered. The similarities included small isolated headwater populations on the west side of the divide. The findings are currently unexplainable to them as well. Definitely science has no answer for this and subsequently no evidence that they are indeed true greenback populations. But since they are just trout, it sure it fun to think of the possiblities that they would exist in Utah. For now, for the sake of fun, let’s leave open the possibility until the door is slammed shut.
For me, I hope that it truly is a greenback population, whose existence might also prove an ancient connection as a founding strain of the most historic colorado cutthroat. What a find this would be!!!
By Steve June 25, 2010 - 10:19 am
After many years of surveying for historic Cutthroat trout populations, it is with great apprehension that I tell you that although Behnke definitely has the right take on the power of the observation tool trumping the reality of what is being observed (genetics), his work itself suffered from incomplete knowledge of the past. It was not necessarily his fault though, as he and other early studiers of Greenback, Rio Grande, and Colorado River Cutthroat meristics and phenotypes were not looking at “historic” populations when they thought they were. The gentetics are what they are, but they have been overextended with statistics and assumtions to say things that really have no meaning.
The missing piece of the puzzle in all of this, is the work done by the U.S. Fish Commission from the 1880′s onward. They kept very good records and I came across recently scanned reports in the NOAA archive which show how the Black-spotted (native cutthroat) were propogated and distributed through Colorado, Utah, Wyoming, New Mexico and elsewhere in the west. Broodstock was mixed very early from both sides of the Divide and housed at the Leadville hatchery with returns of crosses being returned to lakes on both sides of the Divide. Examples are Cutthroat taken from Sweetwater Lake (Colorado River), Black Lake (Blue River), Twin Lakes/Rock Creek (Arkansas) and subsequently Grand Mesa Lakes and Pikes Peak Reservoirs. Progeny of these were placed everywhere on both sides of the divide and in the Rio Grande and up in Wyoming and were shared with other federal hatcheries as they came on line (e.g. Saratoga, WY).
Behnke and early meristics investigators (also, Proebstel) were not dealing with historic populations most likely (although Como Creek was never specifically mentioned in these reports). The reports of Black-spotted distribution reads like a who’s who of previously thought historic populations. The real eye-opener populations that were stocked include: Bear Creek and Severy Creek (recently though pure Greenback), Carnero Creek (thought Rio Grande Cutthroat), all of the Little Snake River in Colorado and Wyoming (thought Colorado River Cutthroat), East Fork Piedra River (thought Colorado River Cutthroat). Basically, all of the populations listed by the State and Local Biologists as historic were planted by the U.S. Fish Commision. This includes all of the populations above natural barriers -several of which were used incorrectly as baselines by early biologists.
They did an amazing job, and I can’t believe the places they went with such “limited” technology and how the fish have prospered for over a century fairly undisturbed. Several populations were placed alongside brook trout and we can see how that played out as well (some cutthroat still do persist).
This is the reason for the “hodgepodge”. This means that there remains nothing “pure” from which to base subspecies. But, apperantly, the earliest musem specimens show that there may not have been much differentiation between the regions in the first place, and what we have left courtesy of the early Fish Commission work may in fact be very close to what was present in the larger rivers of the region when the settlers arrived.
Early reports did mention a unique cutthroat common to the upper Eagle River in Colorado, as an aside.