The Diversity of Trout

DNA study concludes that only the greenback cutthroat trout in Bear Creek (Colorado) closely matched DNA of museum specimens.

November 15, 2021 By James Prosek

The “Riffles & Runs” column of the Feb-Mar 2013 issue described a new DNA study published by Drs. Jessica Metcalf and Andrew Martin. Their study compared DNA samples taken from museum specimens of greenback trout to DNA from extant cutthroat trout populations across Colorado. They concluded that only the greenbacks in Bear Creek closely matched the DNA of the museum specimens. All the other “greenbacks” they sampled were genetically much closer to Colorado River cutthroat trout. The following is a rebuttal of sorts from painter and author James Prosek, who says “the word species—in the way it is used in public, conservationist, and even scientific circles—is insufficient to communicate biological reality.” It is an excerpt from the revised and updated Trout of the World (Abrams, 2013).

In September 2000, driving east from California to Colorado, I decided to stop in the desert to try to catch a native trout called the Humboldt cutthroat. I took Route 50 along Lake Tahoe and then into the desert wasteland, where the air hovered around 100 degrees. I spent the night in Elko, Nevada, lights flashing from casinos, the vibration of trucks on Route 80 shaking the water in the glass on my bedside table.

The next day I drove along the roads outside Elko toward the upper tributaries of the Mary’s River. Rabbitbrush was in flower along the dirt trails, mountains formed up ahead, and a plume of dust behind me obscured what had come before. Antelope congregated around a water hole. A golden eagle flew across the road. I hit a whip-poor-will with my car and stopped to look for it and lament its death.

I was following a publication put out by the state of Nevada in the 1970s, a survey of remaining populations of the native cutthroat trout in these upper tributaries. It looked as if the stream with the greatest abundance of fish was one called Wildcat Creek. I wondered if, some 30 years later, the fish were still there. I followed a topographical map to find it. After turning onto a smaller dirt road on the other side of a cattle guard, I slowed to speak with a man standing by his truck—the only person I’d seen for miles. His name was Bill Gibbs, and he owned the ranch through which Wildcat Creek ran. He was watching yearling cattle that would soon be brought along Route 80 to feedlots in Nebraska. I asked him if he knew about the trout in Wildcat Creek. Would he mind if I fished it?

He said that the summer before, a wildfire had burned on the property and gone right over the creek, and he wasn’t sure if the trout had survived. He pointed to where the creek was. It would be about a mile walk from the road, and I was welcome to fish it.

When I saw the creek after a walk through the hot desert country, it looked like a creek in Hades. I half expected to see a fallen angel crouched beside it. The willows along the bank had been charred black, but there was a small intermittent blue ribbon of water coursing through. It resembled a sliver of sky. And when I peered into the water through the tangle of burned brush, I saw fish, remarkable luminous trout, and not so small, considering that the creek was no more than three feet across in most places.

I used only the top segment of my three-piece fly-fishing rod to dap a fly into small pools that I approached quietly and carefully.

In short order I caught one. Then another, and another. I carefully laid them on my hat to take pictures and then let them go. I made sketches with graphite and colored pencil that might help me remember the pink, purple, and ochre hues that I would try to recreate in the studio. The trout I released were so eager to bite that I probably could have caught each one a second time. I was covered in dust from crawling along the bank, and charcoal lines were drawn on my clothes from the burned limbs of sagebrush and willow and aspen that I’d pushed through as I walked. That evolution could produce such a fish, able to survive what nature had thrown at it for millennia, was remarkable.

We sometimes, correctly, think of nature as fragile. I have described the trout this way, too, and it is indeed vulnerable to rapid alterations of its habitat by humans, from pollution, climate change, or drawing water for irrigation. But all I could think of at that moment was the resilience of nature, the relentlessness of these fish in holding on in an ecosystem that most would consider hostile. I walked back, parched and humbled, to my car, conflicted about having disturbed this place but elated over what I had witnessed.

This, of course, was a personal experience that went beyond what a single name or even theory can impart. People called the fish in these upper tributaries the Humboldt cutthroat trout, related to a fish called the Lahontan cutthroat trout. Individuals argued over whether the Humboldt cutthroat should be given a subspecies name or not. Is it a subspecies? Is it distinct enough a population to be given species status? The question What is that? did not seem the most relevant one to ask. In the desert the only clear answer to me at that moment was: It is. You can argue over what category an individual fish fits into and never come up with a definitive answer—this kind of argument might never be resolved. But one truth you cannot deny is that it exists.

I believe that in the future we will no longer need to answer the question "What category does that fish fit into—what family, order, genera, or even species?" Rather, the relevant questions will be: What is it related to? What is its position in the history of life? How long ago did X separate from Y? I am not a taxonomist, one who spends his life trying to make sense of evolutionary history and then classify accordingly, though I admire that pursuit. My job is easy in comparison. I have set out to create a visual record of biological diversity. Instead of asking "What is that?" I am simply saying, “Here it is.”

Since the publication of the first edition of Trout of the World, great changes have taken place in the communication and collection, retention, and dissemination of information about trout and other creatures on the planet. Not long ago, even as recently as the year 2000, my friends and I planned expeditions by handwriting letters to knowledgeable people in far-off lands and occasionally trying to coordinate a phone call. At that time, if you wanted to learn about a fish like the Humboldt cutthroat trout, there was very little written information and few images available. You had to go see it yourself.

Personal blogs and websites kept by the trout-obsessed, mostly amateur anglers, contain hundreds of photos of native trout, often geo-referenced to the place where they were caught. Such aggregations of information are valuable growing catalogs of biological diversity that—in my opinion, as they accumulate with new knowledge of genetic relationships, behavior, and habitat requirements—will help the importance of certain taxonomic categories fade away. The arguments over what to call fish, I feel, will lose out to an interconnected, complex, reticulate story of life.

More than 60 of the fish shown in Trout of the World represent diversity within a single species—the brown trout, known by the Linnaean binomial Salmo trutta. By painting and presenting them here, I hope I have conveyed that the word species—in the way it is used in public, conservationist, and even scientific circles—is insufficient to communicate biological reality.

Darwin expressed his frustration with the word species and questioned where to draw lines amid infinite beauty and diversity.

“It is really laughable,” he wrote, “to see what different ideas are prominent in various naturalists’ minds, when they speak of ‘species’ . . . It all comes, I believe, from trying to define the undefinable.” In On the Origin of Species, he wrote, “I look at the term ‘species’ as one arbitrarily given, for the sake of convenience, to a set of individuals closely resembling each other.”

Such is the source of my preoccupation—you could even say obsession—with our legacy of naming nature, which started with Adam’s task to name all the creatures in the garden (as the story goes) but is really as old as language itself.

Naming is a necessary act in communicating about the natural world, and an essential part of being human, but it also has great limitations in expressing the real nature of reality—which Darwin exposed to us with his account of the ever-evolving origins of species. Ours is a fluid, continuous, chaotic, and ever-changing world.

The opinions expressed here are those of the authors and do not necessarily reflect the editorial policies or views of Fly Fisherman. We welcome polite reader responses to the issues presented here. The Editor.

James Prosek wrote his first book, Trout: An Illustrated History, while he was an undergraduate at Yale. Since then he has published 11 books, including The Complete Angler, Eels, and Ocean Fishes—the last of which was reviewed in the Feb-Mar 2013 issue. He lives and works in Easton, Connecticut.