Biologists’ fears on the lower Colorado River confirmed

Denver, Colo. ( Associated Press) — For National Park Service fisheries biologist Jeff Arnold, it was a moment he dreaded. Barefoot in sandals, he was pulling a net in the shallow backwaters of the lower Colorado River last week when he saw three young fish that weren’t there. “Call me when you get it!” He messaged a colleague while posing for the photo.

Minutes later, the Park Service confirmed their worst fears: The smallmouth bass had indeed been found and likely regurgitated into the Colorado River below Glen Canyon Dam.

They may be a beloved game fish, but smallmouth bass feast on humpback chub, an ancient, threatened fish native to the river, and biologists like Arnold are working hard to recover. Poachers wreaked havoc in the upper river, but were held at bay at Lake Powell where the Glen Canyon Dam has served as a barrier for years – until now. The recent sharp decline of the reservoir is enabling these introduced fish to move beyond the dam and down into the Grand Canyon, where the largest groups of chub live.

There, Brian Healy has worked with humpback chews for more than a decade and established the Native Fish Ecology and Conservation Program.

“It’s so devastating that you see all the effort and effort you’ve put into removing other invasive species and relocating populations around to protect the fish,” Healy said.

As reservoir levels drop, non-fishers living in the warm surface waters in Lake Powell are drawing closer to the dam and its penstocks—submerged steel tubes that carry water to turbines, where it generates hydroelectric power. and left on the other side.

If bass and other predatory fish are sucked into the penstocks, survive and breed under the dam, they will have an open alley to attack chub and other natives, potentially leading to years of restoration work. Uncovering and elevating the Grand Canyon aquatic ecosystem – the only stretch of river still dominated by native species.

On the brink of extinction decades ago, the chub is back in modest numbers thanks to fish biologists and other scientists and engineers. Agencies spend millions of dollars annually to deter intruders in the upper reaches of the river.

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Under the Endangered Species Act, government agencies are required to operate in ways that “would not endanger the continued existence” of listed animals. Including infrastructure.

Even before the discovery of smallmouth bass spawning under the dam, agencies were prepared for the moment. The US Bureau of Reclamation recently enlisted a team of researchers from Utah State University to map non-fish in Lake Powell. And try to determine who can pass through the dam first.

A task force quickly assembled earlier this year to address the low water urgency for native fish. Federal, state and tribal leaders are expected to release a draft plan in August that includes solutions for policymakers who intend to delay, slow down and respond to the threat of smallmouth bass and other predators beneath the dam.

There are a variety of solutions, but many will require significant changes in infrastructure.

Meanwhile, the National Park Service, the US Geological Survey and Arizona Fish and Game are moving swiftly in trying to control the issue. During an emergency meeting, they decided to step up their surveillance efforts in other shallow areas and closed the entire backwaters where the smallmouth bass were found so that they could not swim in the river.

“Unfortunately, the only block nets we have are very large nets, so it won’t stop these small fish from going in, but it will prevent the adults from going back out,” Arnold said, adding that it’s the best they can do with what’s available. can means.

Experts say that releasing more water into Lake Powell would be the best solution to ensure that cold water is released through the dam, although it is difficult to have that much tension in the river.

Last month, the Interior Department informed states that the Colorado River is dependent on water, meaning the entire southwestern United States, that they must work out a way to save a fifth to a quarter of the river’s supply in 2023. should, or face federal intervention. It’s not clear where the protected supplies will be stored, but Healy says he hopes Lake Powell is being considered.

“If we want to protect some of the values ​​for which Grand Canyon National Park was founded, we really need to think about how water is stored,” Healy said. “That issue needs to be put on the table.”


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