Upper Colorado River Endangered Fish

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A rare species of chub known as bonytail are reproducing naturally in the upper Colorado River system, according to Utah Division of Wildlife Resources (UDWR) biologists.

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 1 to 2 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.)

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.

The last wild adult bonytail were collected in the late 1990s, according to Krissy Wilson, native aquatic species coordinator for the Utah Division of Wildlife Resources (UDWR).

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.

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.

The Endangered Fish Recovery Program is working to recover bonytail, razorback sucker, humpback chub, and Colorado pikeminnow in the Upper Colorado River . More information about the program and its work is available at www.coloradoriverrecovery.org.

source: Utah Division of Wildlife Resources