Office of External Affairs
Mountain-Prairie Region


U.S. Fish and Wildlife Service
Mountain-Prairie Region
134 Union Boulevard
Lakewood, Colorado 80228

May 4, 2010

Contact: Debbie Felker, Recovery Program

                 303-969-7322, ext. 227

              Mark Hadley, Utah Division of Wildlife Resources





LAKEWOOD, Colo. – Endangered Colorado pikeminnow and other native fish in the Green and Yampa rivers in Utah and Colorado show a positive response to the Upper Colorado River Endangered Recovery Program’s efforts to coordinate water releases from reservoirs and to manage nonnative fishes.


Last fall, Recovery Program biologists reported a sixfold increase in the number of young-of-the-year (less than one-year-old) endangered Colorado pikeminnow collected last summer compared to the average catch in the previous 18 years.  That information is specific to a 120-mile reach of the middle Green River below Dinosaur National Monument in northeast Utah.   


Researchers attribute last year’s gain to a combination of higher summer base flows from Flaming Gorge Dam concurrent with a decrease in the number of nonnative smallmouth bass. 


“The higher base flows appear to have created better conditions for these young endangered fish  in backwater areas where they spend their first year of life,” said Recovery Program Director Tom Chart.  “It’s important to recognize that water releases made to help recover the endangered fishes from Flaming Gorge Dam or elsewhere are made in accordance with state and federal water laws and do not affect individual water rights.”


Combined with higher base flows, nonnative fish management efforts have reduced the number of smallmouth bass in the same reaches of the Green River from 60 adult fish per mile in 2004 to about 20 per mile in 2009.  Removing the larger, nonnative fish prevents them from eating the larvae and young Colorado pikeminnow.


Native fish have also responded favorably to a reduction in the number of adult smallmouth bass in recent years in the Yampa River in Little Yampa Canyon, about 10 miles downstream of Craig, Colo.  As smallmouth bass numbers declined, researchers collected more mottled sculpin, a small native fish that lives in shallow riffles.   Researchers also saw an increase of all native fish species combined from only 1 percent of the catch in 2003 to more than 8 percent in 2009.  Although no roundtail chub, another native fish species,  were collected in 2003 and 2004, they now appear in 20 percent of near shore samples. 

“These increases in the number of native fish demonstrate the effectiveness of our work to reduce the number of large-bodied, predatory nonnative fish as well as managing river flows,” Chart said.  “Restoring river habitat and the mix of native fish in the system is an important step toward recovering the endangered Colorado River fishes.”


Starting last month, the Recovery Program resumed nonnative fish management work in 526 miles of the Colorado, Duchesne, Green and Yampa rivers in the states of Utah and Colorado to help recover the endangered humpback chub, bonytail, Colorado pikeminnow and razorback sucker.  Biologists from the Utah Division of Wildlife Resources, U.S. Fish and Wildlife Service (Service), Colorado Division of Wildlife and Colorado State University (CSU) are conducting the work.


In addition to smallmouth bass, the Recovery Program is working to manage nonnative northern pike, another large-bodied, predatory fish.  Past efforts resulted in a shift from large-sized, adult northern pike in a 70-mile reach of the Yampa River to smaller, juvenile fish. Similar reductions of adult northern pike populations have occurred in critical habitat in the Green River where northern pike abundance has decreased by more than 90 percent since efforts began .  The Green River population is linked to the Yampa River, because the majority of northern pike spawning occurs in specific habitats found only in the upper Yampa River drainage. 


Management of smallmouth bass populations is much more complicated.  Researchers are concerned that a large group of smallmouth bass spawned throughout the Upper Colorado River Basin during the low flows of 2007 will reach maturity and spawn this summer.   Sampling crews from the states of Utah and Colorado, CSU and the Service will coordinate upcoming field work to capture and remove as many adult smallmouth bass as possible before they spawn.  


In 2008 and 2009, the entire Upper Colorado River Basin experienced a return to higher and cooler river flows and smallmouth bass reproduction was greatly diminished in all rivers. 


“Predictions for lower than average flows in 2010 favor the nonnative species,” Chart said.  “This means that researchers need to make the most of their sampling efforts while the Recovery Program’s partners do what they can to deliver flows that will help benefit the native species.”


Nonnative fish management is one of many recovery actions that enables use and development of water from the Upper Colorado River Basin to proceed in compliance with the Endangered Species Act (ESA). Since 1988, recovery actions implemented by the Recovery Program have provided ESA compliance for 1,711 water projects depleting more than 2.8 million acre-feet of water in the Upper Basin.


Researchers will also conduct other studies related to endangered fish recovery this year.  These include gathering data to complete estimates on the abundance of Colorado pikeminnow and humpback chub; monitoring floodplain habitat and sediment; and monitoring razorback sucker reproduction through collection of their larvae.  In addition, hatchery-raised bonytail and razorback sucker will be stocked in sections of the Green, Gunnison and Colorado rivers to help reestablish populations.


For more information, contact the Recovery Program at 303-969-7322, ext. 227, or visit the “events and news” tab on the Recovery Program’s website at


The Upper Colorado River Endangered Fish Recovery Program is a cooperative partnership of local, state and federal agencies, water developers, power customers and environmental groups established in 1988 to recover the endangered fishes while water development proceeds in accordance with federal and state laws and interstate compacts.



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