Colorado’s trout fisheries could face a difficult summer, impacting the state’s billion-dollar angling industry, as widespread drought conditions drive predictions that streamflows will be well below-average.

Kirk Klancke, the president of the Colorado Headwaters Chapter of Trout Unlimited, said he is concerned that the drought will stress fisheries this summer, especially if temperatures are anywhere near as elevated as they were this winter.

“If this summer is anything like this past winter was, the chances are pretty good that there’s going to be fish kills in our streams,” Klancke said. “It’s 100% given that, without some miracle monsoon season, we’re going to see (river) temperatures that threaten trout — and fishermen who care will be fishing in the mornings.”

Colorado, and much of the West, experienced one of the hottest, driest winters on record. In March, a climate change-fueled heatwave rapidly melted off the state’s already historically poor snowpack to record-low levels. With little snow left to melt, only about half the normal amount of water is expected to flow through most rivers this summer, and some rivers could see closer to a quarter of the normal flows, according to the latest Colorado Water Supply Outlook report.

Colorado’s angling industry generates nearly $2 billion in total economic output annually and supports over 15,000 jobs statewide, according to the state government. The state has 6,000 miles of streams, including over 360 miles that Colorado Parks and Wildlife has designated as Gold Medal trout fishing, and more than 1,300 lakes and reservoirs. Fly fishing, especially for rainbow and brown trout, is among the most popular forms of fishing in the state.

While every summer has its “ebbs and flows,” Patrick Gamble, a fly fishing guide for Straightline Sports in Steamboat Springs, said anyone visiting Colorado to fish this summer should expect the experience to be a little different that past years.

With the low flows, Gamble said he’s already called a number of his customers who had booked June trips on the Yampa River to reschedule for earlier in the spring, since he doesn’t expect the river to flow later in the summer. As temperatures get hotter heading into the summer, he said anglers should also plan to fish in the cool of mornings, rather than on hot afternoons, or at higher elevations to avoid harming trout populations.

“This year, when you have less water, there’s still as much pressure — just as many eagles, ospreys, more river otters than ever and angling pressure to boot,” Gamble said. “Coming off the lowest snowpack in recorded history, it’s definitely super concerning.”

Drought likely to stress trout populations

With most of Colorado’s rivers expected to experience extremely low streamflows, Klancke said, “we’re really worried this year is going to be really hard to keep fish alive,” especially if there are above-normal temperatures.

When rivers run low, the water is spread thin and warms faster, Klancke explained. That is a problem because hot water holds less dissolved oxygen, which cold-water species like trout — the primary targets of Colorado’s angling industry — need to breathe, he said.

“Your river is built like a solar collector,” Klancke said. “When your flows are depleted, it’s the same width of streambed, but the river spreads out over that width, and it’s very shallow. The rocks collect the heat because they are exposed when the river is shallow. That heats up the river.”

When water temperatures approach 71 degrees Fahrenheit, Colorado Parks and Wildlife public information officer Rachael Gonzales said trout become stressed and will feed less. If conditions are severe enough, Gonzales said the state wildlife agency can issue voluntary or mandatory closures of certain stretches of river. She said aquatic biologists are monitoring the rivers and will determine if actions are needed this summer.

Trout Unlimited and most Colorado fly fishing outfitters recommend anglers stop fishing for trout when water temperatures hit 68 degrees, so as not to harm the fish. Even during a year with a normal snowpack, Klancke said that some streams hit this threshold several days a year.

“At 68 degrees, we tell people to just quit fishing because you can catch a fish and have all the thrill of playing him, getting him in a net, releasing him properly, but when he swims away, he’s expended so much energy he can’t recover,” he said. “At 68 degrees, it really becomes catch and kill, instead of catch and release.”

Anglers stress ethical fishing during drought year

While anglers hope the period of wetter, cooler weather Colorado has seen over the last couple of weeks continues, long-term forecasts suggest the West could be in for a hot summer.

Over the next three months, western Colorado is likely to see above-normal temperatures and average to slightly-below average precipitation, according to the National Weather Service’s Climate Prediction Center.

“The most important message for this summer is, if you’re a catch-and-release fisherman, fish with a thermometer and know what temperatures threaten trout,” Klancke said. “It’s not just water conservation in a drought year, it’s how we handle our fisheries and keep these fish alive.”

Across Colorado, Trout Unlimited and other conservation groups are working to educate visitors about the drought conditions and how hot water can impact trout. This summer, Klancke said the Colorado Headwaters Chapter will launch into “high gear” radio and newspaper education campaigns and volunteers leaving flyers under the windshields of vehicles parked along rivers in Grand County on hot days.

The warmer it gets this summer, the fewer “easy-access” trout fishing locations there will be in the lower Yampa Valley, Gamble said. But that doesn’t mean there won’t be any fishing; it just means anglers may have to move to higher elevations, where temperatures are cooler.

“Being trout-centric in the state of Colorado, you definitely epitomize a hot summer day with a dry fly and searching a river bank with a grasshopper fly,” Gamble added. “But, sometimes that just means you need to be up at 9,000 feet, instead of down at a valley floor at 7,000 feet, to find water that releasing a trout in is ethical.”

Gonzales said that in addition to starting early and avoiding warm water, it is also important to not overcrowd an area. She suggested anglers also target warm-water species of fish, like pike, which face fewer impacts during hot weather. 

Because the vast majority of Colorado’s fly fishing guides are ethical anglers and won’t fish in conditions that stress fish, Klancke said many fly fishing guides may work mornings only on hot days. If this summer sees extended periods of warmth, he said that could have ripple effects across the industry.

“This is particularly hard on our guides because our guides now are going to half day,” he said. “Think about it — they’re going to have their income cut in half. … To have your work hours cut in half is just really hard on professional guides.”