Were Greenbacks Really Discovered in Utah?

Greenback/Chris Anderson

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.


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