Lake trout

A large, deep-water char with a forked tail, native at Glacier but an invasive species anglers must kill on sight in Yellowstone and Grand Teton lakes.

Lake trout at a glance

Salvelinus namaycush Salvelinus namaycush is sal-VEL-ih-nuss nam-ay-KUSH

Type
Fish · trout
Diet
Carnivore
Size
Adults commonly run larger than the 18- to 22-inch native cutthroat trout they compete with; the Wyoming state record weighed about 50 pounds, as much as a full bag of dog food.
Lifespan
Commonly lives 20 to 25 years in the wild.
Conservation
Least concern overall; native but imperiled (Montana state rank S2) in its home range at Glacier, and killed on capture as an invasive species in Yellowstone Lake and Grand Teton's Jackson Lake.

Eats cutthroat trout, whitefish, sculpins, insect larvae, zooplankton

It hunts in deep, cold water, and where it has invaded, it eats other fish, including native cutthroat trout up to a third its own length; even when its favorite prey runs scarce, it can survive for years on whatever else the lake offers.

Should you worry?

None to a person. In Yellowstone Lake, every lake trout caught must be killed on the spot; it is illegal to release one alive. Never leave the carcass on the shore, since it draws bears.

Twenty-one lake trout came up in a single overnight gillnet set on Yellowstone Lake in 2007, at a time when cutthroat numbers had already crashed. Inside those 21 fish, biologists counted the remains of at least 47 cutthroat trout. Hauls like that are why crews have spent every summer since trying to kill lake trout faster than the lake can make more.

Lake trout are not native to Yellowstone Lake. In 1890, the U.S. Fish Commission stocked them on purpose into Lewis and Shoshone lakes, two other lakes in the park. More than a century later, on July 30, 1994, a 17-inch lake trout turned up in a net in Yellowstone Lake itself. Exactly how they got there is not certain. A lake trout can live 20 to 25 years, and one big enough to eat cutthroat eats a lot of them.

The response has been relentless ever since. In 2023 alone, six boats set and lifted more than 5,000 miles of gillnet, about a fifth of the way around the Earth, and killed 236,853 lake trout. Over the past 28 years the total tops 4.5 million. Catch one yourself in Yellowstone Lake and the rule is not catch and release: puncture the air bladder, drop it in water as deep as you can find, and never leave the carcass on the shore, because it will pull in a bear.

Did you know?

  • Lake trout were stocked into Yellowstone's Lewis and Shoshone lakes on purpose in 1890, decades before anyone confirmed they had reached Yellowstone Lake itself, in 1994.
  • A lake trout can survive for years on very little food because it is cold-blooded, which is part of why it is so hard to remove once it establishes in a lake.
  • At Glacier National Park, lake trout are native, but only in the handful of waters that drain toward Hudson Bay. Everywhere else in the park's lakes, it arrived on its own, swimming up from the lower Flathead River, where it was stocked in the early 1900s.

Common questions

What do lake trout eat?

Mostly other fish, including native cutthroat trout up to a third their own length, plus insect larvae and zooplankton when fish are scarce.

Are lake trout native to Yellowstone?

No. They were stocked into other Yellowstone waters in 1890 and turned up in Yellowstone Lake in 1994, where they are an invasive species that anglers must kill.

How big do lake trout get?

Many grow larger than Yellowstone's native cutthroat trout; the Wyoming state record weighed about 50 pounds.

Can you keep a lake trout you catch in Yellowstone Lake?

You do not have to keep it, but you cannot release it alive. Every lake trout caught there must be killed.

What eats a lake trout?

In Lake Superior, the non-native sea lamprey, a parasitic fish, preyed on lake trout. Together with overfishing, it caused a sharp drop in the lake trout catch in the 1950s.

Where it lives

Where we got this