For the first time since work to recover bonytail started in the 1980s, they’re raising their own young in the wild, officials with the Utah Division of Wildlife Resources say.
Bonytail are the rarest of the endangered fish that live in the upper Colorado River system.
“This finding represents a major step forward in recovering the species and ultimately getting it removed from the federal endangered species list,” Krissy Wilson, native aquatic species coordinator for the DWR, said in a statement.
In spring 2015, researchers with the DWR found adult bonytail in Stewart Lake near Jensen. 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.
As the researchers analyzed their data, they expected the young-of-the-year chubs to be roundtail chubs. But they realized the size of the chubs did not fit with the timing of when the roundtail chubs would have spawned.
“That’s when the researchers got excited,” Wilson said. “Were the specimens they were examining the first documented evidence of bonytail reproducing in the wild?”
The researchers sent the preserved specimens to the Larval Fish Laboratory at Colorado State University. There, scale and body measurement analysis was done. Next, the specimens were sent 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 DWR’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 benefitted most from the releases. It’s exciting to see that the releases are also benefitting 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 coloradoriverrecovery.org.