Experimental Effort to Benefit Native Fish Being Expanded In Grand Canyon

Media Contact: Barry D. Wirth, (801) 524-3774
Dennis Kubly, (801) 524-3715

For Release: August 15, 2003

An experimental effort by the Glen Canyon Dam Adaptive Management Program to benefit the endangered humpback chub in a small section of the Colorado River in the Grand Canyon is being expanded. Humpback chub have been affected by a variety of factors such as dam operations, cold-clear water, competition and predation by nonnative fishes, and diseases.

Trout and other non-native fish are known to feed upon native humpback chub, which is an endangered species. The experiment entails removing these species of fish to give humpback chub a better chance at survival and hopefully, increased reproduction and recruitment.

The area being targeted is in a portion of the Grand Canyon seldom fished by anglers, other than river rafters. The current project area is 10 miles long and approximately 60 miles downstream from Lees Ferry, which is a renowned trout fishery below Glen Canyon Dam. The proposed modification would expand the experiment seven miles downstream, to a point 12 miles below the mouth of the Little Colorado River.

The experiment responds to specific Adaptive Management Program goals that include maintaining a quality rainbow trout fishery at Lees Ferry while protecting and enhancing native fish populations downstream of Lees Ferry. It also responds to National Park Service management policies that favor native species within national parks. The removal effort is designed to benefit native fish downstream from Glen Canyon Dam without impacting the tail-water trout fishery.

The experiment was developed and recommended to the Secretary of the Interior by the Adaptive Management Work Group, a Federal advisory Committee that includes 25 stakeholders made up of Federal agencies, State agencies, Native American Tribes and non-governmental organizations, as part of the ongoing Glen Canyon Dam Adaptive Management Program. It is being implemented by the Bureau of Reclamation, U.S. Geological Survey and National Park Service. The research is being conducted by U.S. Geological Survey's Grand Canyon Monitoring and Research Center based in Flagstaff.

The initial portion of the experiment was conducted this year from January through March and resulted in removing 7,573 fish, with 6,703 of them rainbow trout. There were also 130 brown trout and 135 common carp removed.

The non-native fish removal experiment is part of the adaptive management process. This is just one small reach of river in the 277-mile Grand Canyon, but the effort has been more successful than originally anticipated. This unexpected success has led scientists to recommend downstream expansion of the project. If successful, the expansion should increase the amount of improved habitat for humpback chub by removing predators.

"Now we will have to monitor to determine if reduced non-native numbers result in a benefit to the humpback chub. That's why it is called adaptive management. You try something, if it works, you can repeat or expand the process to achieve greater results. If it doesn't work, you move on and try something else," said Steve Gloss, a scientist with the U.S. Geological Survey.

Scientists say the worst that can happen is that trout and other non-native fish are removed from a small segment of river that is in the heart of a national park and seldom fished. The advantage of this operation is it can be done now, does not require any elaborate ecosystem alterations and there is little likelihood of encountering unknown and unwelcome environmental surprises.

The government agencies and groups cooperating in the Glen Canyon Adaptive Management Program include the Bureau of Reclamation, Western Area Power Administration, Bureau of Indian Affairs, Arizona Game and Fish Department, U.S. Fish and Wildlife Service, Navajo Nation, San Juan Southern Paiute Tribe, Hopi Tribe, National Park Service, Hualapai Tribe, Southern Paiute Consortium, Pueblo of Zuni, Southwest Rivers, Grand Canyon Trust, Grand Canyon River Guides, Federation of Fly Fishers, the seven basin states of Arizona, Colorado, New Mexico, Utah, California, Nevada and Wyoming, the Colorado River Energy Distributors Association and Utah Associated Municipal Power Systems.

The endangered humpback chub is one of eight native fish species that were once abundant in the 277-miles of river flowing through the Grand Canyon. The humpback chub is a "big-river" fish that grows to 20 inches. It is superbly adapted to survive in the wild and turbulent Colorado River that had historic flows ranging from 500 to 300,000 cfs. Small eyes protect it from swirling silt.

Scientific monitoring data for the last ten years indicate that HBC populations have declined. Those declines have been due to a variety of factors, such as dam operations, habitat alteration, predation and competition with nonnative fishes, and parasites.

Experimental Actions to Help Native Fish and Lees Ferry Trout Fishery

The Glen Canyon Dam Adaptive Management Program http://www.usbr.gov/uc/envprog/amp/ was formed in 1997 to advise the Secretary of the Interior on actions to improve resources in Glen and Grand canyons.

In January 2003, the Glen Canyon Dam Adaptive Management Program began an experiment to remove non-native fish from the Colorado River in the Grand Canyon.

The experiment had two thrusts. One was releasing experimental high-fluctuating flows from the Glen Canyon Dam to disrupt the non-native trout spawn in the Grand Canyon and to attempt to improve growth and condition of the Lees Ferry trout fishery. The other was physically removing non-native trout near the inflow of the Little Colorado River in the Grand Canyon, some 60 miles downstream of Lees Ferry.

One objective of the experiment is to reduce the number of non-native fish that prey on and compete with the federally endangered humpback chub in this reach of river near the Little Colorado River.

Why Extend the Experiment 7 Miles?

Increasing the magnitude of the treatment offers the best chance of obtaining an unambiguous experimental result. The extension will affect a larger portion of the area where humpback chub and non-natives are believed to interact and possibly result in increased survival of juvenile chub.

Young humpback chub entering the main stem of the Colorado River from the Little Colorado River (LCR) almost exclusively occupy habitat downstream of the LCR. They are more vulnerable to predation when they leave the warm, muddy LCR and enter the cold, clear Colorado River. The cold water from Glen Canyon Dam makes it difficult for small native fish to swim, and also severely limits their growth.

The removal area upstream of the LCR is intended as a buffer to reduce the likelihood of immigration downstream by non-native fishes. Extending the removal downstream by seven miles could potentially more than double the improved habitat for young humpback chub and result in improved survivorship.

If the experiment is successful we expect to see improved survival of humpback chub and an increase in their population size. It could take three to four years to see such an increase.

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Relevant Link:

Glan Canyon Dam Adaptive Managment Program