During breeding, male bonytail turn bright red on the belly. Photo © John White
An Imperiled Native Fish
The bonytail is the rarest of the endangered fish species in the Colorado River Basin, and is thought to be nearly extinct upstream of Lake Powell. Threats to the bonytail include flow regulation, habitat loss and alteration, competition with and/or predation by exotic fishes, and water pollution in the Colorado River Basin. Selenium, a heavy metal often found in runoff from disturbed sites, including uranium mines, can affect reproduction in fish (including the endangered Colorado River fish) and may bioaccumulate, impacting species higher in the food chain like river otters and bald eagles.
Natural History
Historically, bonytail were present in the Colorado River system, which includes the Yampa, Green, Colorado and Gunnison rivers. Today, there are no known populations in Colorado. A handful can be found in the Green River drainage in Utah, while slightly larger populations exist in Mohave Reservoir on the Arizona-Nevada border. Most bonytail are now produced in fish hatcheries, with the offspring released into the wild when they are large enough to survive in the altered Colorado River system environment. Dark on top and pale on bottom, bonytail are well adapted hide from predators in the murky waters of the Colorado River. They are opportunistic feeders, eating insects, zooplankton, algae, and plant matter. Bonytail prefer eddies, pools, and backwaters near swift current in large rivers.
Conservation Status
-Endangered Species, Endangered Species Act, 1980
-Colorado Division of Wildlife Endangered Species
-Utah Species of Special Concern
Action Taken
We monitor and challenge inappropriate development projects in the upper Colorado River watershed, including uranium mining, oil and gas drilling, and water diversion projects, to protect this rare species and water quality in the Colorado River basin.
