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.
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