But this is a drought year, and a confluence of extreme conditions now threatens the state’s legendary waters. Higher temperatures early in the year, worryingly low river levels, fish die-offs and pressure from the crush of anglers yearning to recapture a year lost to the pandemic have swirled into a growing crisis. This week the state announced a slate of new restrictions, including outright closures, for some of the top trout streams. And a new coalition of businesses, fly fishing guides and environmentalists warned that the severe drought may not be a temporary problem and that the state’s fisheries could be nearing collapse. The coalition, which includes Orvis, the fly fishing company, and the clothing manufacturer Patagonia, sent Gov. Greg Gianforte a letter Wednesday seeking the creation of a task force to address the decline of the fisheries. “Between early season fish kills, unnaturally warm water temperatures and low trout numbers, it’s an all hands on deck moment,” said John Arnold, owner of Headhunters Fly Shop in Craig, along the Missouri River, one of the state’s premier fisheries. The coalition said that the conditions not only threatened the fisheries, but also would be devastating for businesses. “If water quality in our rivers continues to decline, and our rivers themselves dry up, these negative changes will also tank our state’s robust outdoor economy that directly depends on upon vibrant cold water fisheries,” the group stated in its letter. “This is a really unique, ecologically speaking, part of the world,” said Guy Alsentzer, the executive director of Upper Missouri Waterkeeper. “These rivers are really hurting and they need cold, clean water.” The crisis is occurring as the state was just beginning to recover from the pandemic, with tourists and fishing enthusiasts returning in large numbers. Anglers of all kinds spend nearly $500 million a year in Montana, according to the American Sportfishing Association. In addition to low river levels and even dry sections of some small streams, dead trout have been found floating in rivers around the state, a sight that in other seasons was rare. And there has been a mysterious, steep decline in one of the most sought-after fish, brown trout, over the last several years in southwest Montana. Trout thrive in water between 45 and 60 degrees. Temperatures in some rivers have hit the low-70s much earlier than usual. At those temperatures the fish are lethargic because there is less oxygen in the water and they quit feeding; the stress of being caught by fishers in that weakened state can kill them. About 75 degrees can be lethal to trout. Montana’s rivers and streams are wild trout fisheries, which means that unlike in most states, rivers there are not stocked with hatchery-reared trout. If populations crash, the state’s wild trout would have to rebound on their own, which could take years or might not happen at all. Low flows and warm temperatures are affecting sport fishing across the West, from California to Colorado. On the Klamath River in Northern California, the Iron Gate Fish Hatchery could not, for the first time in its 55-year history, stock the river with young hatchery-reared salmon and steelhead because extremely low flows and warmer water temperatures have increased infections from C shasta, a parasite. Utah has doubled the allowable limit for fishers because low water levels are expected to kill many fish in the streams. In Colorado, state officials asked people not to fish a 120-mile-long stretch of the Colorado River in the north-central region because of low river levels and warmer water. “The water temperatures have been above 70 degrees for multiple days in a row,” said Travis Duncan, a spokesman for Colorado Parks and Wildlife. “And there is a potential for more closures as we get further along in the season.” On Tuesday, the Montana Department of Fish, Wildlife and Parks imposed “hoot owl” restrictions on the Missouri River, one of the most popular trout fishing sites in the state, between Helena and Great Falls because of warm water temperatures. The rule bans fishing after 2 p.m. (The term “hoot owl restrictions” stems from the early days of the timber industry. Loggers work early in the mornings of late summer, when it’s cooler, because the forests are dry and that increases the risk of chain saws or other equipment sparking a fire. Loggers often heard owls during their early morning shifts.) Yellowstone National Park announced that, beginning on Saturday, it would shut down fishing on its rivers and streams after 2 p.m. until sunrise the following day, citing water temperatures exceeding 68 degrees and extremely low river flows. “These conditions are extremely stressful and can be fatal to fish,” the park said in a news release. Although restrictions are often put in place at some point in the summer season, this year is unusual. “From what we know historically, this is unprecedented in the extent” of limits that have been imposed, said Eileen Ryce, the administrator for the state’s fisheries division. Compounding the situation here is the decline over several years in brown trout populations in the southwestern part of the state, including the Big Hole, Ruby, Yellowstone, Madison and Beaverhead Rivers, some of the top destinations for fly fishers. This year on the Big Hole River, for example, on one of the most popular stretches, a May census found 400 brown trout per mile, down from 1,800 in 2014. The Beaverhead River has dropped to 1,000 from 2,000 brown trout per mile. And those counts were conducted early in the season, before the onset of this summer’s extreme conditions. The state is considering long-term restrictions on all of these rivers, which could include release of all brown trout or shutting down fishing in some places. What, precisely, is causing the decline over such a large regional area of the Upper Missouri River Watershed is stumping experts, especially since brown trout are traditionally a hardy, resilient species, able to handle warmer temperatures. Many attribute the decreases, at least in part, to shifting river conditions caused by climate change. Oddly enough, an unintended benefit of the raging wildfires in the West has been the smoky skies, which may be keeping the rivers from getting even warmer by reducing the amount of direct sunlight. Meanwhile, on the Beaverhead and Bitterroot Rivers, anglers have reported seeing fish with large lesions whose cause is still unknown. Beyond hoot owl limits, those who fish have been asked to rapidly land their catch and carefully and quickly release them, to minimise the stress of handling and reduce the potential for killing them. Other factors threatening Montana’s trout include agricultural changes. Ranchers used to primarily flood irrigate their fields, which returned about half the water to the river system. Now many use pivot irrigation systems, which are far more efficient and use nearly all of the water. “We may have altered groundwater so much that brown trout haven’t been able to adapt,” said Patrick Byorth, the director of Trout Unlimited’s water project for Montana. The group is a nonprofit focused on fisheries. Water pollution also adds to the problem. Increasing construction near resort areas along the Gallatin River near Yellowstone National Park, for instance, has contributed, with stormwater runoff and septic systems sending phosphorus and nitrogen into the Gallatin River, causing algae blooms. The bloom is exacerbated by warmer temperatures and lower flows. One big question that can’t be answered is whether this is just a bad year, or a part of a more permanent change in the climate, a long-term aridification of the West. Arnold, the fly-fishing guide who has worked on the Missouri River for decades, said the decline in trout populations has been occurring over a longer span of time than just this year. “My top guides could put 60 fish in the boat in a day,” he said. “Now half of that would be considered a good day.” “It’s all climate-change related,” Arnold said. Twenty years ago, nobody fished in November and March because it was so cold, he recalled. Now they do. “It’s starting to feel like a downward spiral.” © 2021 The New York Times Company