A GREAT FISH; A NATIVE FISH

©By Susan B. Eirich, Ph.D.

Sometime about 100,000 years ago, here in our area, there was a split in trout evolution. Sixty chromosomes became 64 and a new subspecies came into being - one supremely adapted to our local environment: the Yellowstone cutthroat trout. It is the only indigenous trout in the Teton Watershed. Once abundant, it is now largely limited to the South Fork of the Snake River, and our own Teton River and its tributaries. This scrappy, pioneering member of the salmon family found its way into our area past all obstacles and adapted. These fish are ancient, they are unique and they are native.

 In 2003 anglers on the Teton River sent direct expenditures of $700,000 into our economy. Prized by fishermen from around the world, the anglers who come here are willing to pay up to 50% more for the privilege of fishing for our cutthroat trout. Because they evolved in waters that aren’t really productive, they make the most of their marginal habitat, aggressively eating any food that that comes by – including the offering of the dry fly fisherman. They are able to survive on smaller prey and adjust their size to the available food supply, making it possible to live in the food-poor tributaries that feed the Teton River. This beautiful, fighting fish can live up to 11 years.
 
They have evolved to the specific stream flow patterns natural to the Teton Valley, with a sharp peak in June as the snow melts high in the mountains. The water flows strongly through the system, then slows at the end of the melt. The cutthroats evolved in this snowmelt rhythm - high, high water, then low, low water on an annual cycle. They migrate and spawn in tributaries during the high water in June. The female fans her powerful tail to make a nest in the gravel as males compete to fertilize the eggs. As the flow begins to slow and the turbulence decreases, the eggs begin to hatch and the fry migrate out to the stream edge habitat among the cobbles, banks and bars. The young fry hide among the cobbles, gravel and woody debris where they are protected from the full force of the current. Historically some fish would migrate to the river, then fight their way back up the tributaries – Teton Creek, South Leigh, Darby Creek, Fox Creek, to spawn again where they were born. Others would spend their entire lives high up in the small tributaries.
 
It is much more difficult for trout to access the tributaries now. Under the law of unintended consequences, before we began to realize how interconnected everything is in nature, we changed the water flow patterns in the valley. The middle portions of Darby, Fox, Teton and South Leigh Creeks are often completely dewatered and the Teton River population is isolated from those that remain in the upper tributaries in the mountains. The water is diverted as soon as it leaves the mountain ranges. Instead of flowing through the stream channels much of the water is spread out via a network of irrigation channels. This decreases the peak flows and creates a more uniform year round flow in the lower portions of these streams. The more uniform flow is better suited to the non-native trout such as the rainbow and the eastern brook trout, both brought in through stocking. In addition the brook trout spawn the preceding fall, and thus their fry, having a size advantage, are suspected of invading areas where the young cutthroat hang out in what once was relative safety, displacing them, out-competing them for food and possibly feeding on them. Many of the tributaries, historically important cutthroat spawning areas, are now full of brook trout. According to a new study by Rob Van Kirk of Idaho State University, just out January 2005, one of the changes necessary to recover the cutthroats is restoration of natural flows and floods in streams traditionally dominated by snowmelt runoff.
 
Cutthroats are decreasing over their entire range so dramatically that they are under consideration for listing under the Endangered Species Act. The Teton River and the South Fork are two of the last best strongholds…but the Teton River showed a 95% decline in a survey done by Fish and Game in 2003. Few young ones were seen. In a double whammy, the cutthroat hybridize with the non-native rainbows resulting in mongrel  “cutbows.“ As the cutthroats decrease, they find mates more easily among the rainbows, and these hybrids then continue to interbreed through the generations with each other, with rainbows and with cutthroats, leaving fewer and fewer genetically pure fish. 

Researchers are uncertain about the percentages for each of the various possible factors at play – habitat loss, drought, altered stream flows, disease, lack of connections between tributaries and the mainstem….…. or if the population will  rebound. Fish and Game will do another survey in the Teton River this year. Although the research is in its infancy, it gives us pause for thought as we develop the valley, for there is a sad and ironic twist with a possible tiny silver lining. As we lose our farms and ranches and open space, and subdivisions sprout, hydrologists suggest it is possible we will be diverting less water and the streams will flow in a more natural way again – if we haven’t built in their flood plains and consequently decide to manipulate the peak flows protect our houses. Thus, if we want to preserve our native fish it is crucial to preserve remaining, and in the future restore, potential habitat. Only 3% of historical cutthroat habitat still has strong pure populations protected from non-native species. Two creeks in our area are part of that 3% - the upper portions of South Leigh and Darby Creek, and the lower portions were probably excellent cutthroat spawning before they were dewatered. The valley sections of South Leigh and Darby still have ideal spawning habitat: cottonwoods shade and cool the water, stabilize the banks, create fallen woody debris that protect the fish from predators and rushing currents, and create channels, pools and riffles. There are long stretches of stream between the foot of mountains and where groundwater springs well up closer to the river that are potential spawning habitat.  South Leigh has perhaps the strongest remaining cutthroat population, in its upper reaches in the national forest and mountains. The fact that historically South Leigh (and other streams)  was in all likelihood dry during portions of the year even before altered stream flows, is not necessarily a deathblow for its having been (or becoming again) a cutthroat spawning stream in its valley section. The fish would simply migrate back to the river as the tributaries dry out, as there are no obstacles to their movement. Sizeable fingerlings were seen just above Highway 33 in South Leigh two years ago.
 
The cutthroat, Oncorhynchus clarki bouvieri, is named after Clark who first described it during his expedition with Lewis. The name refers to the red slashes on their lower jaw. Emotions run deep when fishermen speak of days spent on the river catching these beautiful feisty wild fish. They speak of how precious the fish are to them. Of  memories fishing with granddad. They speak of clients coming from elsewhere where fishing is depleted; where only stocked fish are available, and who find it close to magic that there are still naturally reproducing wild populations. Clients who speak of what much of the rest of the country has lost; of incredible treasure we have that must not be taken for granted and thus not protected. They speak of the joys of catching native fish doing its own thing. Fish that have evolved to this climate and set of circumstances, and survived through thick and thin; the native fish that have been here forever, in tune with its habitat.
 
We still have a chance if we do not build in the floodplains of the tributaries and allow the necessary high water floods  – the same floods that have given us our world-class cottonwood bottoms. Those cottonwood bottoms that harbor the great gray owls and a myriad other forms of life. We, the brook and the rainbows have other places to live. The cutthroats do not, and we have choices and decisions to make.

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