For many western fly-fishermen, climate change is hitting too close to the snow-fed trout rivers they call home: trout populations are declining throughout the interior west as water temperatures rise, habitat ranges shift and buckle, and stream ecosystems collapse. In fact, recent studies conducted by federal agencies and trout conservation groups predict that by century’s end climate change will decrease suitable trout habitat in the American west by 50 percent or more. Indeed, the impacts of climate change on trout are as clear and chilling as the water in which the fish have tenaciously survived since the Pleistocene, one million years ago.

Less clear, however, is how waning trout populations will impact the state and local economies that derive millions of dollars from trout-related recreation every year. Local trout shops, guides, and outfitters rely on the health and stability of trout fisheries. However, climate change has increased the frequency and intensity of winter flooding, summer drought, and forest fires. And it is unclear if these businesses will be able to adjust quickly enough to compensate.

Climate change for trout begins high above their river residences. Mountain snow pack, a frozen, natural reservoir of the cold, clear water that nourishes trout streams and their piscine populace is decreasing. The chief cause is a rapid rise in western air temperatures. According to the Rocky Mountain Climate Organization, a non-profit coalition of businesses and environmental groups, the five-year average temperature for Montana, Wyoming, Idaho, and Colorado is two degrees higher today than it was in those states a century ago.

As the air warms, precipitation patterns change. More snow now falls as rain in the winter, which leads to smaller mountain snow packs. Normally, snow pack melts incrementally during the spring and summer, providing rivers a constant supply of cold, clear water. But smaller average snow packs mean that western states are not getting the mountain water storage they need to maintain stream flows during the year. Bruce Farling, Executive Director of Montana Trout Unlimited, says that for eight of the last ten years Montana has seen below average stream flows. On top of that, he says, severe droughts, which plague nearly every western state, are preventing beleaguered streams from being naturally replenished by spring and summer rains.

Decreased stream flows directly affect trout, which depend on cold water to survive. Less water means less suitable habitat for fish because shallow water heats up faster. “All salmonids (a family that includes trout, salmon, and whitefish) have pretty limited temperature ranges,” somewhere between 50 and 65 degrees Fahrenheit, says Jeffrey Kershner, Director of the United States Geological Survey’s (USGS) Northern Rocky Mountain Science Center in Bozeman, Montana. At these temperatures, water contains enough dissolved oxygen for adult trout to respire or “breathe” and for young trout to develop. Beyond 60 degrees, however, dissolved oxygen decreases, and trout begin to suffocate.

Ominously, climate models indicate that surface water temperature in many western rivers and streams will increase if air temperatures rise beyond 5.4 degrees Fahrenheit. In fact, scientists predict a rise in average air temperatures anywhere from 5-10 degrees by the end of the century, according to the NRDC.

Dwindling snow packs indirectly influence trout populations as well. Consistent supplies of snow pack runoff helps reduce the frequency and intensity of forest fires. “When forests dry out, wildfire activity picks up,” says Jack Williams, Senior Scientist for Trout Unlimited. “This can have some serious ramifications for trout fisheries.” Intense forest fires burn away the vegetation that anchors soil and sediment in place. This liberated sediment can enter streams in large quantities and muddy up the clear, oxygenated water that trout eggs require for development.  Streams containing more than 15 to 20 percent of fine sediments like silt or clay, Williams says, threaten trout eggs. “The sediment gets into spaces between gravel and the eggs die from lack of oxygen.”

As diminished snow packs melt earlier and faster, many western states now experience more frequent and powerful spring and winter flooding. These floods are the combined result of rapidly melting snow pack and increased winter rains when there should be snow. They can devastate fall-spawning species like brown and bull trout, which lay their eggs in river gravel during the fall to over-winter for a few months before hatching in the spring. Frequent and intense winter and spring flooding effectively scours the eggs from the river bottom, killing the un-hatched fish in a roil of sediment and stones.

As trout populations suffer, however, so too will the trout angler’s experience and all of the businesses inspired and supported by that experience.   According to the American Sport Fishing Association, the country’s 40 million anglers produce nearly $50 billion in retail sales a year. In 2002, Colorado sport fishing supported more than 10,000 jobs and generated nearly $800 million for the state. And in Montana, angling produces nearly $300 million dollars for the state, annually.

Most of this money is generated during the summer when vacationing tourists seek refuge from their sweltering cities and flock to the cool, trout-filled rivers of the Rocky Mountains. But as the West warms, peak trout fishing season shifts to months when people can’t take vacation. “Most out-of-state anglers are geared to fishing June through September,” says Dave Kumlien, outfitter and owner of Troutfitters fly shop in Bozeman, Montana. “You might have a handful of hard core guys who can come and fish earlier but most people just can’t do that.”

This seasonal shift is largely the result of prolonged and widespread summer fishing closures on western rivers. These closures are instituted by the Department of Fish, Wildlife, and Parks (FWP) when water temperatures exceed the thermal limits of a river’s trout population. From 2001 to 2007, the FWP ordered161 fishing closures in Montana alone.

In July of 2007, for instance, hundreds of rainbow and brown trout died when temperatures in Yellowstone National Park’s Firehole River reached 82 degrees Fahrenheit. The event prompted a highly publicized river closure that many guides say deterred potential clients. That’s because river closures, which generally begin in the afternoon, force anglers to begin their day well before the sun comes up. This is a problem for guides whose clients would rather cancel their trips than get up at 5:00 a.m. to accommodate closures.

Other fishermen will cut their trips in half.  But “Half days equal less tackle and less equipment which means less money coming in,” Kumlien says.  In addition, the quality of fishing in rivers warm enough to warrant closures is generally poor since the thermally stressed trout are sluggish and weak. Consequently, summer tourists cancel their trips and truck their rods to cooler, Canadian waters where trout are in better shape. This adversely impacts western fly-fishing businesses that depend on the summer tourism to keep them financially healthy during the off-season.

Changes in insect hatches also promote a seasonal shift. The emergence of mayflies, a primary trout food, coincides with the tail end of peak runoff and, Williams says, the insects have been shown to emerge earlier in warmer water. So, as rivers warm and runoff peaks sooner, mayflies that normally hatch in June and July are now emerging in March and April. “When popular hatches shift to these earlier months”, says Kumlien, “people don’t come in the same numbers they used to and you have fewer guides and outfitters running around.”

Ultimately, climate related changes restrict trout habitat, and less habitat means fewer fish. Over time, trout will retreat to higher, cooler tributaries to escape the starving flows of the West’s progressively tepid main stems. As a result, easily accessible and heavily-fished rivers like the Madison in Montana and the North Platte in Wyoming may empty of fish and, hence, fishermen. Over time, guides and their clients may have to travel farther to find fish. And because the higher elevation streams to which trout populations will move are narrow, steep, and more difficult to access, outfitters may be pushed out of the float-fishing business.  Similarly, prolonged drought, violent runoff and flooding will make boat access to floatable rivers more challenging.

Scientists are only just beginning to quantify the economic impacts associated with climate change; so much is left to speculation.  But the trout that swim beneath the West’s imperiled rivers and the anglers who cast feathered trickery upon them can’t wait for calculation. “If we wait for hard and fast numbers to act it’s going to be too late,” says Farling.

Williams believes the best way to mitigate climate change impacts on trout and their associated economies is to manage river systems responsibly; to ensure that trout are not forgotten in our rush to seize water for irrigation, recreation, and cities.  “One of the most important things we can do,” he says, “is to make sure river systems are in good quality. Because those that are in good shape can withstand the disturbances associated with climate change and they will be able to bounce back.”

After all, fly-fishing is not simply a past time. For many western states, it is a way of life, a western heritage built on blue-ribbon trout streams and supported by family-owned fly-shops and outfitters. Protecting these businesses and the millions of dollars that trout angling generates begins by protecting the resource: the beautiful and boisterous beasts caught in the swift current of a changing climate.

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