National Geographic Daily News
Yellowstone cutthroat trout spawn.

Yellowstone cutthroat trout (pictured) are declining thanks to pressure from larger invasive lake trout.

Photograph by Jay Fleming

Cathy Newman

For National Geographic News

Published January 22, 2013

It's a case of trout versus trout, and in the face-off between native Yellowstone cutthroats (Oncorhynchus clarkii bouvieri) and the intruders on the scene, lake trout (Salvelinus namaycush), the judgment handed down is a no-brainer. The lake trout must go.

The problem, explained Pat Bigelow, a fisheries biologist at Yellowstone National Park, Wyoming, emerged in 1994 when lake trout were discovered in Yellowstone Lake. Why lake trout were introduced into the lake is a mystery. Perhaps, biologists speculate, some anonymous angler wanted to diversify the fish population in the lake but didn't think through the consequences. "It's an example of bucket biology," said Todd Koel, supervisory fisheries biologist for the park. (Related pictures: Trout vs. Trout in Yellowstone Lake.)

A Yellowstone cutthroat—coppery in color, back peppered with spots, a blush of pink by the gills—is a thing of beauty. But it is outmatched in size and outlived by the lake trout, which weighs in at over 50 pounds (23 kilograms) and can reach the ripe old age of 20-plus years, about twice the span of cutthroats. More to the point, lake trout eat cutthroats.

Why the fuss? Isn't variety the spice of trout fishing? Not at all, said Bigelow. The cutthroat fishery provides an estimated 34 million dollars in economic benefit to the area. Lake trout—not as easy to catch—are no substitute for their native cousins. More important, Yellowstone cutthroats, and their genetic well-being, need protecting. Two of fourteen cutthroat species—the Alvord and yellowfin—are already extinct. (Related interview: Invasive fish species in the Great Lakes.)

There are other factors that speak to the wisdom of weeding out non-natives. Lake trout are deepwater dwellers and inaccessible to the otters, ospreys, bears, and eagles that prey on easily caught, shallow-water-dwelling cutthroats. Ten years ago, Koel pointed out, there were 50 nesting pairs of ospreys in the lake system area. Today there are only three or four.

Once the alien species was discovered, the Park Service was quick to respond. It started netting the intruders and in the past ten years has hired commercial fishermen to accelerate the process with large deepwater entrapment nets. Last year, more than 300,000 lake trout were removed from the lake, pushing the ten-year total take to about a million.

But lake trout aren't going away any time soon. Netting has slowed down, but not completely solved, the problem. "The war isn't won yet," said Koel. "It's a matter of keeping ahead of the curve."

19 comments
Mark River
Mark River

Why don't we start eating them.I'm a river guide on the Mississippi River in the delta. We have a so-called invasive species called the Asian and silver carp. I grew up eating grass carp and these species have the same bony structure that most people have discarded because we have gotten so use to boneless fish. If you scur them properly and fry them in hot olive oil or peanut oil they are really tasty. Those trout would probably be tasty smoked over hickory wood or steamed smoked under willow leaves. Come to the delta and take a trip with myself and John Ruskey at Quapaw Canoe Company. Go to www.island63.com and www.rivergator.org and plan a trip. Save all the rivers!

robin poole
robin poole

The Lake Trout are ruining fishing in the Lake and the River. Lake trout provide little diversity in fishing. They don't fight!! The remaining cutts in the system are now bigger but hardly exist. It used to be I'd take a "new" fisherman to The Yellowstone becuase the fish were so easy to catch. The Lakers have taken care of that. Can't comment on taste as I do Catch & Release, not keep and eat. Down with the Lakers!!!!.

Uday Thambimuthu
Uday Thambimuthu

@Mark River no offense to your local cuisine, but one should never fry with olive oil, especially extra virgin. Olive oil is better for simmering and adding to pastas and salads, high temperatures cause it to burn and release toxic byproducts

Eric Lane
Eric Lane

@robin poole I seem to have no problem catching hundreds of cutthroat throughout the season as a fishing guide on the lake.  Sure the cutthroat fishery isn't as good as it used to be, but I'm not sure of a more reliable place to catch 3+lb cutthroat as reliably and easily as Yellowstone Lake.

It is a dire situation, to be sure, but it's not gone yet.  The Lakers meat is generally pink like salmon.  Most of us guides don't even bother with the lakers that have white meat.

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