Saving Bull Trout

By Tom Sentner

A juvenile bull trout swims through the water above a juvenile cutthroat trout.
A juvenile bull trout swims through the water above a juvenile westslope cutthroat trout in Glacier National Park.

USGS

Immersed in a cathedral-like forest of tall trees in the cool quiet of morning, my thoughts are interrupted upon hearing an unfamiliar sound behind me—horse hooves. I am hiking the trail to Quartz Lake, where I’ll interview Glacier National Park’s fisheries crew. I had fallen behind the lightning-paced crew and now I’m falling behind the mules packing in their supplies, even though the animals are loaded down with inflatable kayaks, nets, fuel, and other supplies. Fisheries management work in Glacier’s backcountry is fraught with logistical challenges, and I start to think maybe I shouldn’t have packed my inflatable bed roll and those heavy cans of chili.

Finally, I reach Quartz Lake. The crew is busy re-packing the mules with the previous week’s worn nets and empty gas containers. Their newly acquired boat, flown in by helicopter last year, sits anchored on the glassy water in front of imposing Vulture Peak. There’s a good reason why Fisheries Program Manager Chris Downs focuses much of his team’s efforts here. This quiet lake, ringed by dense, coniferous forest, is a key battleground in the fight to save some of the last viable bull trout populations and habitat in the Northwest.

Bull trout are the top native predators of the upper Columbia River system. They have a very low thermal tolerance, meaning they require extremely cold water to survive. This makes bull trout vulnerable to warming stream temperatures, which are predicted to continue to rise as the climate warms. They are also a migratory species that moves from lakes and rivers into smaller tributaries to spawn, making them additionally vulnerable to the loss of suitable stream habitat. Nonnative lake trout, which spawn directly in lakes, displace bull trout through predation and competition for food. These combined threats create a challenging conservation puzzle for Glacier’s fisheries team.

Glacier National Park records show that concern about the invasive nature of lake trout was voiced in the 1930s and again in the 1960s by fisheries biologists studying Glacier’s lakes and streams. These concerns proved to be tragically valid. Lake trout, which had been intentionally introduced to Flathead Lake in 1905, gradually made their way into the upper reaches of the watershed, including lakes on Glacier’s western slopes. Bull trout populations that thrived in these waters for thousands of years crashed rapidly, with dramatic declines often appearing within 30 years after initial detection of lake trout. Quartz Lake is unique among these lakes. When lake trout were first documented in Quartz Lake in 2005, the lake still contained a healthy bull trout population. Biologists feared that if immediate action wasn’t taken, the bull trout population would essentially disappear, mirroring what had occurred in all of Glacier’s other large lakes west of the Continental Divide.
Fisheries crew member throws gill net out from boat as two crew members look on.
Gill netting for lake trout began in Quartz Lake in 2009.

NPS/Jacob Frank

To save the Quartz Lake bull trout population, focused efforts have been made to remove lake trout with gill nets, simulating the commercial fishing pressure that historically caused the collapse of lake trout fisheries in the Great Lakes. These efforts are also being applied at nearby Logging Lake, where the U.S. Geological Survey (USGS) is testing lake trout netting as a long-term strategy for bull trout recovery. In addition, park managers and USGS researchers teamed up to try something new and experimental—moving juvenile bull trout upstream from Logging Lake to Grace Lake to try and establish a new bull trout population.

Logging Lake was historically home to one of the most robust bull trout populations in the park. But when lake trout showed up, the population crashed. Translocating, or moving, bull trout upstream to Grace Lake is a way to put some of the bull trout population in “the bank,” so to speak, and protect it until lake trout can be removed from Logging Lake. As Glacier fisheries biologist Carter Fredenberg explains, “The reason we chose Logging and Grace is because there is a natural barrier between the two lakes, keeping Grace Lake protected from invading lake trout. We were at the very last stages of where we thought bull trout might become extirpated from Logging Lake if something was not done, so we got together with USGS and said, ‘Let’s move fish!’ ”
At the inlet to Logging Lake, 111 juvenile bull trout were captured using backpack electrofishing equipment. The young trout were then put into garbage bags filled with water that had been supersaturated with oxygen and cooled by ice packs. Finally, the bags went into backpacks that were then hiked to the Grace Lake inlet. The idea was to move some of the last remaining members of this population into a safe location above the falls, while gillnetting as many lake trout as possible in Logging Lake, driving that population down. The hope is that many of the bull trout established in Grace Lake can be moved back into Logging Lake once the habitat is more suitable for their success.

But saving a species takes more than just figuring out how to move fish. It requires integrating bull trout recovery with the overall management of Glacier National Park. For example, state and federal laws require the control of invasive species—but Glacier’s fisheries biologists must also, by law, take care to preserve the wilderness character of the park. Wilderness concerns have to be reconciled with the team’s critical mission to save the bull trout, a species that is federally listed as threatened and a fish that has a key role to play in the ecology and cultural landscape of the park.

The fisheries team doesn’t net lake trout during peak visitor months, so as not to detract from visitors’ wilderness experience. They also avoid disturbing other species that share these areas with the bull trout. “We take care to avoid impacts to wildlife like loons and eagles, and are constantly working to minimize bycatch of other fish species in the lake trout removal nets. We pay attention to behavior and do everything we can to limit disturbance to those critters,” says Downs. “It’s a balancing act. We try to make the best decisions we can with the information we have at the time.”

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Western tanagers flit through the trees as we follow the trail over a steep ridge and through thick patches of thimbleberries to the crew’s cabin on the shores of Quartz Lake. As soon as we’re finished setting up camp, our next task is to hike to nearby Lower Quartz Lake to set nets. On the hike down, we take a quick detour so crew member Jon McCubbins can show me the fish barrier that was constructed between Quartz and Lower Quartz lakes to keep new lake trout from invading.

The barrier consists of gabions (bales of rock held together with wire). The ingenious design of the barrier is that the gabions are placed in such a way that water flowing through them does not form deep pools. Without deep pools, fish cannot get enough speed to jump the barrier. “Since the barrier was built in 2005, we’ve definitely been putting the hammer down on lake trout,” Jon says. The crew has removed thousands of lake trout from Quartz Lake since then, and is now seeing the fruits of their labor. Each year, they find more redds, which are the nests bull trout build in streams. This is a good sign, because successful lake trout control should lead to recovering bull trout populations. As Jon explains, “We saw the highest redd counts ever the year before last, and almost as high last year. We hope that is a reflection of what we’re doing with the lake trout, and that lake trout numbers have been going down. Last year I think we only caught 17 adults.”

These encouraging results are what make tackling all the challenges of such a complex conservation puzzle worthwhile. No one knows how the story will end, but we do know that bull trout have adapted to this unique landscape over millennia and that they are an important species worth fighting to save. If this crew has their way, bull trout will be swimming these cold, clear headwaters for generations to come.
Researcher holds adult bull trout
Native bull trout have adapted to this unique landscape over millennia.

USFWS/Jim Mogen

Last updated: February 6, 2018