In Northwest Montana, Recreational Fishing for Bull Trout is a Catch-22

For the past 20 years, the road to recovery for Montana’s apex native fish species has included a rare recreational opportunity for anglers to target bull trout on two local waterbodies in the Flathead Valley, the Hungry Horse Reservoir and the pristine South Fork Flathead River. Listed as threatened under the Endangered Species Act in 1998, bull trout populations have faced a steep decline on a landscape brimming with introduced species, which have radiated throughout the Flathead River system and decimated native trout species. But the South Fork remains isolated from those competitive pressures below Hungry Horse Dam, creating one of the most productive wild trout fisheries in North America.

And yet, the stressors on bull trout in the South Fork persist, particularly as climate change has depressed stream flows, warmed water temperatures and disrupted migratory patterns. That confluence of factors has led recently to the lowest bull trout population counts in the South Fork since 1993, alarming fisheries managers tasked with the species’ recovery and prompting a suite of proposed changes to the upcoming year’s fishing regulations.

“The reality is, these fish are facing lots of stressors,” Leo Rosenthal, the fisheries management biologist for Montana Fish, Wildlife and Parks (FWP) in Region 1, said. “We’ve had low flows and warmer stream temperatures these last few years, but many of the typical stressors that we’ve identified as having the biggest impacts on bull trout in the Swan and Flathead River systems are directly related to nonnative species. And we don’t have that in the South Fork or in Hungry Horse Reservoir. Bull trout don’t have predators like lake trout and northern pike to compete with. And while we can’t control the climate, the one thing we do have control over is the number of native fish that are allowed to be caught and released out there.”

When bull trout received ESA protections in 1998, most Montana waters were closed to recreational bull trout fishing. In 2004, however, portions of the South Fork and Hungry Horse Reservoir, as well as Lake Koocanusa, were reopened to catch-and-release fishing through a permit with the U.S. Fish and Wildlife Service (FWS), with harvest opportunities for two bull trout annually on Hungry Horse. Rosenthal has monitored the success of those angling opportunities using a catch card system, which requires anglers record their bull trout catch throughout the fishing season. Anglers are then sent a survey at the conclusion of the season and the data is entered and summarized by FWP staff. Recent surveys have revealed an increase in the number of anglers focusing their bull trout fishing in the wilderness segment of the South Fork as well as closer to Hungry Horse Reservoir. And although the South Fork fishery is limited to catch-and-release fishing, “there is concern for handling stress impacting the population,” Rosenthal said.

On Nov. 12, the Montana Fish and Wildlife Commission’s vice chairman, Pat Tabor, will carry four amendments to the 2025 Fishing Regulations on FWP’s behalf, including limiting intentional angling for bull trout on the South Fork to a month-long period from July 1 to July 31. The current season begins on the third Saturday in May and runs through July 31. And while Rosenthal said it’s by no means a foregone conclusion that the Fish and Wildlife Commission’s seven members approve the new angling regulations, he hopes they will appreciate the urgency of his request.

“We want to narrow the season and reduce the amount of handling. The reason for that is we know these fish come out of the reservoir in the spring and migrate into the South Fork to spawn, and we want to give them every opportunity to get up the river,” Rosenthal said, referring to the section of the South Fork from Crossover Boat Ramp to Meadow Creek Pack Bridge. “There’s a lot of angling use during that period.”

Indeed, 60% of all bull trout that are caught occur in the lower portion of the South Fork, while 40% of bull trout are caught in May and June. In 2023, Rosenthal said he recorded an estimated 973 bull trout caught and released in Hungry Horse Reservoir and the South Fork Flathead River, with the latter accounting for 582 bull trout.

“So this proposed change would cut out 40% of the fish being caught in the South Fork, according to our catch card estimates from last year,” Rosenthal said, emphasizing the high return rates of the catch card surveys.

Other proposed changes would prohibit all angling from June 15 to Sept. 30 within a 300-yard radius around the mouths of Little Salmon and Gordon creeks, which are two spawning tributaries of the South Fork, and around the inlet of Big Salmon Lake. The final proposed change would reduce the number of bull trout anglers are allowed to harvest annually, from two to one.

“Our data show that harvests are already very low, with an average of about 50 bull trout harvested from Hungry Horse Reservoir annually,” Rosenthal said. “This would cut that in half.”

For Rosenthal, as well as other fish ecologists and anglers in the region, the proposed changes to fishing regulations aren’t meant to be permanent; rather, they’re an opportunity to determine how much of an impact angling pressure is exacting on the local bull trout populations.

“We feel it’s important to keep bull trout on the landscape as a valued sport fish,” Rosenthal said. “The overarching goal of this package of amendments is to make sure we still have this fishery for future generations.”

Wade Fredenberg, the FWS’ former bull trout recovery coordinator for the region, and the current president of the Flathead Valley chapter of Trout Unlimited, remembers engineering the catch-card system with Rosenthal two decades ago.

“When we started collaborating on the catch cards, the argument was that the biggest threat to bull trout in our area are these nonnative fish that have been spread around, so our thinking was that if we can make people value bull trout from a sport-fishing perspective, that would at least blunt some of the incentive of bucket biologists to plant other fish where we don’t want them,” Fredenberg said. “I don’t think that thinking has changed. But part of our assessment was that a healthy bull trout fishery like what we had in the South Fork could withstand that kind of angling pressure. If that is no longer true, that’s troubling.”

Clint Muhlfeld, an aquatic ecologist for the U.S. Geological Survey’s Northern Rocky Mountains Science Center, said the South Fork Flathead River represents “the last of the best for bull trout,” and that developing research supports the need to conserve it as some of the most intact habitat in the lower 48.

“The South Fork really represents Montana’s natural heritage where we have this protected watershed that’s got cold, clean, complex and connected habitat,” Muhlfeld said. “This migratory populations of bull trout swims from Hungry Horse Reservoir up the South Fork and into the Bob Marshall Wilderness to spawn. Ecologically, it’s the best stronghold for bull trout and other native species in the northern Rockies. And recreationally, it’s one of two places in Montana where you can still legally fish for bull trout. That’s unique, to have a recreational fishery for a threatened species.”

“There’s only so many levers these fisheries managers can pull as management tools to help the populations rebound, and tweaking these fishing regulations is really the only tool available on the South Fork because it’s in a wilderness area,” Muhlfeld added. “This is one tangible management action they can take to try and reduce mortality, and with the redd counts at the lowest on record since 1993, we have to let them try.”

For Rosenthal, the need to dial back the recreational angling opportunities came into focus this fall, when for the second time in as many years fisheries biologists observed a dramatic drop in the number of bull trout spawning beds, known as redds, in the South Fork.

“The trips to do these surveys is no small task, but it’s the best data we have for adult bull trout abundance,” Rosenthal said. “Because of the logistics, we only monitor the wilderness section of the South Fork every three to five years. But last year we did a survey that showed really low numbers, so we went back again in 2024 to confirm that it wasn’t a fluke or a one-off. And what we found this year was even lower numbers, the lowest we’ve recorded going back to 1993.”

In 2006, Rosenthal said fisheries biologists counted 588 redds in the South Fork’s eight tributaries, while this year they only counted 171 redds.

“The redd counts in the South Fork are 30% what they were in 2006,” Rosenthal said. “That’s why we’re asking for these changes. It’s the one thing we can control.”

“In the case of the South Fork, we like having this recreational fishery for bull trout,” he continued. “It keeps bull trout relevant as a desirable sport fish. These are the largest trout species we have that are native to Montana and they are also an iconic species ecologically. This proposal is a compromise of not wanting this fishery to go away. It’s a compromise that we hope will lead to being able to preserve them as a sport fish and minimize the stress of handling them for conservation purposes.”

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