In The Rockies, Climate Change Spells Trouble For Cutthroat Trout | KUOW News and Information

In The Rockies, Climate Change Spells Trouble For Cutthroat Trout

Apr 18, 2017
Originally published on April 18, 2017 6:39 am

There's an unplanned experiment going on in the northern Rocky Mountains. What's happening is that spring is arriving earlier, and it's generally warmer and drier than usual. And that's messing with some of the fish that live there.

The fish is the iconic cutthroat trout. It's a native North American fish that thrives in cold, small streams. Explorer Meriwether Lewis of Lewis and Clark Expedition fame was among the first European-Americans to catch this spangly, spotted fish. He used deer spleen as bait.

It's relative rarity now makes it a favorite for catch-and-release anglers. But biologists have now found that it's in danger. The much more common rainbow trout is invading cutthroat streams and mating with the native fish. Ecologist Clint Muhlfeld says that creates hybrids.

"It jumbles up the genes that are linked to the locally adapted traits that these fish have evolved with," says Muhlfeld, who's with the U.S. Geological Survey and the University of Montana's Flathead Lake Biological Station.

Those traits have allowed cutthroats to survive through millennia in cold northern streams. And cold streams were thought to protect them from rainbows, which prefer warmer water.

But climate change is warming many high-altitude streams, and they frequently have less water, another change that favors rainbows. So they're moving in.

Muhlfeld says that when rainbows and cutthroats breed, the resulting hybrids are feeble — "less fit," in biological terms. "They don't survive as well as the native fish," he says. And hybrids that do survive continue to make more hybrids; there's no going back to making cutthroats again.

Writing in the journal Global Change Biology, Muhlfeld and a team of scientists from several research institutions studied fish in hundreds of locations in the northern Rockies. Hybridization was widespread. It was most common in places where fish and game departments have introduced rainbow trout, a practice that goes back to the 19th century.

Some states are trying to solve the problem by getting rid of rainbow trout. That might not please some anglers, but Muhlfeld says the cutthroat species could disappear otherwise.

"There are so many places around the world where you can go catch a rainbow trout," he says; it's been introduced all over the world. "There's very few places where you can actually go and catch a native fish that's been around for thousands and thousands of years.

"Extinction is permanent. Once the native genomes and adaptive traits are gone, they are gone forever."

Copyright 2017 NPR. To see more, visit http://www.npr.org/.

DAVID GREENE, HOST:

Now we have a story of an unplanned experiment that is underway in the northern Rocky Mountains. Spring is arriving earlier there. And it's generally warmer and drier than before. And that is messing with some of the fish that live there, including the cutthroat trout.

Now, from its name, you might expect the species would survive any competition but that is not the case as we hear from NPR's Christopher Joyce.

CHRISTOPHER JOYCE, BYLINE: The cutthroat trout is a native North American fish that thrives in cold, small streams. In 1805, explorer Meriwether Lewis of Lewis and Clark fame wrote about catching these very fine trout using deer spleen as bait.

The cutthroat's relative rarity now makes it sought after by anglers as well as biologists. And biologists have now found that it's in danger. The much more common rainbow trout is invading cutthroat streams and mating with the native fish. Ecologist Clint Muhlfeld says that creates hybrids.

CLINT MUHLFELD: It jumbles up the genes that are linked to these locally-adapted traits that these fish have evolved with.

JOYCE: Traits that have allowed cutthroats to survive through millennia in cold northern streams. Many of those streams are getting warmer because of climate change and have less springtime water, conditions the rainbow trout thrive in. Muhlfeld, who's with the U.S. Geological Survey, says when rainbows and cutthroats breed, the resulting hybrids are feeble.

MUHLFELD: They don't survive as well as the native fish. Another reason is there's not a lot of places that you can go and enjoy and appreciate a native fish anymore.

JOYCE: As they report in the journal "Global Change Biology," Muhlfeld and scientists from several research institutions studied fish in hundreds of locations in the northern Rockies. Hybridization was widespread. It was most common in places where fish and game departments have introduced rainbow trout, a practice that started in the 19th century.

Some states are trying to solve the problem by getting rid of rainbow trout. That might not please some anglers but Muhlfeld says otherwise the cutthroat species could disappear.

MUHLFELD: There are so many places around the world that you can go catch a rainbow trout. There's very few places that you can actually go and catch a native fish that has been around for thousands and thousands of years.

JOYCE: Christopher Joyce, NPR News.

(SOUNDBITE OF CLOUDKICKER'S "GARAGE SHOW") Transcript provided by NPR, Copyright NPR.