Changes Push Native Montana Trout Toward Extinction: Study
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[May 28, 2014]
By Laura Zuckerman
(Reuters) - Climate changes that have made
Montana streams much warmer over the last 30 years are helping invasive
trout push their native cousins toward extinction, researchers said on
Tuesday, saying study is an example of global warming reducing
The study led by ecologists with the U.S. Geological Survey links
warming streams and reduced spring flows in the Flathead River basin
in western Montana and Canada to a sharp rise in interbreeding
between rainbow trout introduced by government fishery managers and
native westslope cutthroat trout.
The study, published in the latest edition of the journal Nature
Climate Change, shows evidence that a warming planet could decrease
biodiversity by supporting cross-breeding between invasive and
native species, authors said.
Rainbow trout, stocked in Rocky Mountain streams and lakes to lure
anglers, fared better than westslope cutthroat during a warming
trend in the Flathead basin that saw summer water temperatures
nearly triple between 1978 to 2008, the study shows.
Like other invasive fish, rainbows have greater tolerance for
environmental alterations like lower stream flows because of drought
while native trout adapted to local conditions that historically
brought colder water in greater volumes.
Variables such as habitat degradation were the focus of previous
research on the impact on climate changes on native fish in the
western United States.
While hybridization is a well-established threat to native cutthroat
trout in western North America, the study led by USGS ecologist
Clint Muhlfeld and others demonstrated how factors such as rising
water temperatures influence evolutionary processes by accelerating
interbreeding with rainbow trout and corrupting the natural genetic
pool that allowed westslope cutthroat to adapt and survive in local
streams for more than 12,000 years.
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“Hybridization was a time bomb waiting to go off under the right set
of conditions,” Muhlfeld said.
Cross-breeding reduced the overall fitness of the native fish,
likely decreasing the resiliency and adaptive capacity that helped
it survive cataclysmic events like glaciation, researchers found.
“If these nonnative rainbow trout populations persist, we think the
writing is on the wall and there will be the loss of these native
cutthroat trout, a genomic extinction,” Muhlfeld said.
(Editing by Cynthia Johnston and David Gregorio)
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