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Biologists’ fears confirmed on the lower Colorado River

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Juvenile smallmouth bass sit at a Nationwide Park Service laboratory close to Web page, Ariz., Friday. The nonnative predator fish has made its manner by the Glen Canyon dam and seem to have spawned within the decrease Colorado River, the place it could actually prey on humpback chub, an historic native fish they’ve been working to reestablish. (Jeff Arnold, Nationwide Park Service by way of AP)

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DENVER — For Nationwide Park Service fisheries biologist Jeff Arnold, it was a second he’d been dreading. Naked-legged in sandals, he was pulling in a web in a shallow backwater of the decrease Colorado River final week, when he noticed three younger fish that did not belong there. “Give me a name while you get this!” he messaged a colleague, snapping pictures.

Minutes later, the park service confirmed their worst worry: smallmouth bass had in actual fact been discovered and have been probably reproducing within the Colorado River beneath Glen Canyon Dam.

They might be a beloved sport fish, however smallmouth bass feast on humpback chub, an historic, threatened fish that is native to the river, and that biologists like Arnold have been working onerous to recuperate. The predators wreaked havoc within the higher river, however have been held at bay in Lake Powell the place Glen Canyon Dam has served as a barrier for years — till now. The reservoir’s current sharp decline is enabling these launched fish to get previous the dam and nearer to the place the most important teams of chub stay, farther downstream within the Grand Canyon.

There, Brian Healy has labored with the humpback chub for greater than a decade and based the Native Fish Ecology and Conservation Program.

“It is fairly devastating to see all of the onerous work and energy you have put into eradicating different invasive species and translocating populations round to guard the fish and to see all that effort overturned actually rapidly,” Healy stated.

As reservoir ranges drop, nonnative fish that reside in heat floor waters in Lake Powell are edging nearer to the dam and its penstocks — submerged metal tubes that carry water to generators, the place it generates hydroelectric energy and is launched on the opposite facet.

A Utah State University research team works at Lake Powell on June 7, in Page, Ariz.
A Utah State College analysis crew works at Lake Powell on June 7, in Web page, Ariz. (Photograph: Brittany Peterson, Related Press)

If bass and different predator fish proceed to get sucked into the penstocks, survive and reproduce beneath the dam, they may have an open lane to assault chub and different natives, doubtlessly unraveling years of restoration work and upending the Grand Canyon aquatic ecosystem — the one stretch of the river nonetheless dominated by native species.

On the point of extinction a long time in the past, the chub has come again in modest numbers because of fish biologists and different scientists and engineers. Companies spend thousands and thousands of {dollars} yearly to maintain intruders in test within the higher portion of the river.

Beneath the Endangered Species Act, authorities businesses are required to function in methods that won’t “jeopardize the continued existence” of listed animals. That features infrastructure.

Even earlier than the invention of smallmouth bass spawning beneath the dam, businesses had been bracing for this second. The U.S. Bureau of Reclamation not too long ago enlisted a crew of researchers at Utah State College to map the nonnative fish in Lake Powell and attempt to decide which may move by the dam first.

A job pressure rapidly assembled earlier this 12 months to handle the urgency the low water poses for native fish. Federal, state and tribal leaders are anticipated to launch a draft plan in August containing options for policymakers who intend to delay, gradual and reply to the specter of smallmouth bass and different predators beneath the dam.

There are a selection of options, however many would require important modifications to infrastructure.


If we wish to shield among the values for which Grand Canyon Nationwide Park was established, we have to actually take into consideration how water is saved.

–Brian Healy, founding father of the Native Fish Ecology and Conservation Program


Within the meantime, Nationwide Park Service, U.S. Geological Survey and Arizona Sport and Fish are shifting rapidly to attempt to include the problem. Throughout an emergency assembly, they determined to extend their monitoring efforts in different shallow areas and block off all the backwater the place the smallmouth bass have been discovered to allow them to’t swim out into the river.

“Sadly, the one block nets we have now are fairly massive mesh, so it won’t cease these smaller fish from going by, however it would preserve the adults from going again out,” Arnold stated, noting it is one of the best they’ll do with out there sources.

Consultants say leaving extra water in Lake Powell could be one of the best answer to make sure cool water will be launched by the dam, though it is powerful to do in a river underneath a lot stress.

Final month, the Division of the Inside notified states that rely on Colorado River water, which implies all the southwestern United States, that they need to devise a technique to preserve one fifth to at least one quarter of the river’s provide in 2023, or face federal intervention. It’s unclear the place that conserved provide could be saved, however Healy says he hopes Lake Powell is being thought of.

“If we wish to shield among the values for which Grand Canyon Nationwide Park was established, we have to actually take into consideration how water is saved,” Healy stated. “That subject must be on the desk.”

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