Center for Biological Diversity

For Immediate Release, March 10, 2023


Taylor McKinnon, Center for Biological Diversity, (801) 300-2414,
Sandy Bahr, Sierra Club Grand Canyon Chapter, (602) 999-5790,
John Weisheit, Living Rivers and& Colorado Riverkeeper, (435) 260-2590,
Kyle Roerink, Great Basin Water Network, (702) 324-9662,

Glen Canyon Dam Operations Must Safeguard Grand Canyon’s Rare Fish, Conservationists Warn

Fish Recovery Requires Planning Now for Lake Powell’s Climate Demise

FLAGSTAFF, Ariz.— The U.S. Bureau of Reclamation must manage Colorado River flows to prevent non-native smallmouth bass populations from establishing, thereby jeopardizing threatened humpback chub in the Grand Canyon, conservationists warned in formal comments submitted today.

“Losing the Little Colorado River population of humpback chub would be catastrophic for the fish’s survival and recovery,” said Taylor McKinnon with the Center for Biological Diversity. “This is an emergency situation. The Endangered Species Act requires the Bureau of Reclamation to ensure river flows that maximize protections for these imperiled fish by preventing predatory smallmouth bass from ever taking hold in the Grand Canyon.”

Most remaining humpback chub live at the confluence of the Colorado and Little Colorado rivers. Climate-driven declines in Colorado River flows and historically low Lake Powell levels have caused warm water and smallmouth bass to begin passing through the dam into the Colorado River. If they take hold in the Grand Canyon, smallmouth bass would be impossible to control and would likely wipe out the chub’s last, largest population, which is the source for other Grand Canyon populations.

“It is sad to think that Grand Canyon might lose this important aspect of its ecology, the humpback chub, one of the few native fish species that is still holding on in this portion of the Colorado River,” said Sandy Bahr, director of Sierra Club’s Grand Canyon Chapter. “We just cannot sit back, the Bureau cannot sit back, and let that happen. It must act decisively, and it must act now to address operation of the dam to keep the bass from establishing downstream and to save the chub.”

Today’s comments on a draft environmental assessment urge the Bureau of Reclamation to ensure flows from Glen Canyon Dam are cold enough to prevent any smallmouth bass reproduction downstream. Hydropower interests are urging less protective flows that only disrupt bass reproduction. The filing also calls for long-overdue intake screens or other dam modifications to block passage of non-native predator fish from Lake Powell into the Grand Canyon.

The comments warn that federal agencies must begin planning now for endangered fish recovery in a warmer, drier climate. That includes an always-warm Colorado River flowing through the Grand Canyon, when greenhouse gas pollution and declining Colorado River flows inevitably cause Lake Powell’s surface to fall below what’s required for hydropower production.

“It’s deeply concerning that four decades of endangered fish recovery has arrived at this very dire moment,” said John Weisheit, conservation director of Living Rivers and Colorado Riverkeeper. “It’s past time for federal agencies to plan for endangered fish recovery in the context of the coming day when Lake Powell ceases to exist and sediment-rich warm water again flows regularly through the Grand Canyon.”

The current humpback chub emergency comes less than two years after the U.S. Fish and Wildlife Service, relying on the health of its now-threatened Little Colorado River population, downlisted the fish’s status to threatened from endangered. The decision was sharply criticized for ignoring effects of climate-driven Colorado River declines.

“The emergency now unfolding in Grand Canyon makes a mockery of the chub downlisting decision and shows the danger of climate-reactive recovery planning,” said McKinnon. “Recovery programs for the Colorado River’s endangered fish need to get out in front of climate change disruptions. The status quo of playing catch-up is a recipe for extinction.”

RSHumpbackChub_GeorgeAndrejko_Arizona GameAndFishDept_FPWC
Humpback Chub, Gila cypha. George Andrejko, Arizona Game And Fish Department, Grand Canyon Monitoring and Research Center. Image is available for media use.

The Center for Biological Diversity is a national, nonprofit conservation organization with more than 1.7 million members and online activists dedicated to the protection of endangered species and wild places.

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