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Rare Fish Spawns in the Wild for the First Time

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Biologists have some exciting news about the rarest of the endangered fish that live in the upper Colorado River system. For the first time since work to recover bonytail started in the 1980s, they’re raising their own young in the wild.
“This finding represents a major step forward in recovering the species and ultimately getting it removed from the federal Endangered Species list,”
says Krissy Wilson, native aquatic species coordinator for the Utah Division of Wildlife Resources.
In spring 2015, Matthew Breen, Dr. Robert Schelly and Randy Staffeldt, researchers with the UDWR, found adult bonytail in Stewart Lake near Jensen, Utah. The lake is a managed floodplain that’s connected to the Green River. When the floodplain was later drained in the fall, the
researchers found 19 young-of-the-year native chub. The tiny chub ranged from 1½ to 2½ inches in length.
As the researchers analyzed their data last winter, they expected the young-of-the-year chubs they found in Stewart Lake to be roundtail chubs. As the researchers reviewed the data, though, they realized the size of the
chubs did not fit with the timing of when the roundtail chubs would have spawned. (Young-of-the-year roundtail chubs would have been larger.)
“That’s when the researchers got excited,” Wilson says. “Were the specimens they were examining the first documented evidence of bonytail reproducing in the wild?”
The researchers sent the preserved specimens to Dr. Kevin Bestgen and Darrel Snyder at the Larval Fish Laboratory at Colorado State University. There, scale and body measurement analysis was done. Next, the specimens were sent to Dr. Wade Wilson at the U.S. Fish and Wildlife Service’s Southwestern Native Aquatic Resources and Recovery Center in Dexter, New Mexico, for genetic testing.
Both analyses confirmed what the UDWR researchers were hoping: the specimens were bonytail.
Wilson says the last wild adult bonytail were collected in the late 1990s.
Since then, bonytail have been reared at the UDWR’s Wahweap State Fish
Hatchery at Lake Powell. The bonytail are reared to 12 inches long before being stocked in the upper Colorado River system.
Wilson says for the past four years, the Upper Colorado River Endangered
Fish Recovery Program and its partner, the Bureau of Reclamation, have coordinated spring releases from Flaming Gorge Dam to connect floodplain
habitats along the Green River near Jensen. Connecting the floodplains provides important nursery habitat for the endangered Colorado River fish.
“So far,” Wilson says, “razorback sucker is the species that’s benefited most from the releases. It’s exciting to see that the releases are also benefiting bonytail.”
Along with bonytail and razorback sucker, humpback chub and Colorado pikeminnow are the four fish the Upper Colorado River Endangered Fish Recovery Program is working to recover. More information about the program and its work is available at www.coloradoriverrecovery.org.

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