August 19, 2022
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Biologists try to save ancient fish as Colorado River fades

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PAGE, Ariz. (AP) — Barrett Friesen steers a motorboat towards the shore of Lake Powell, with the Glen Canyon Dam towering overhead. Pale “bathtub rings” line the canyon’s rocky face, starkly illustrating how water ranges have slumped within the second-largest U.S. reservoir amid rising demand and a multi-year drought.

The Utah State College graduate pupil and colleagues are on a mission to save lots of the humpback chub, an historical fish underneath assault from nonnative predators within the Colorado River. The reservoir’s decline might quickly make issues worse, enabling these launched fish to get previous the dam to the place the largest teams of chub stay, farther downstream within the Grand Canyon.

Getting ready to extinction a long time in the past, the chub has come again in modest numbers because of fish biologists and different scientists and engineers. However an rising risk turns into evident in early June as Friesen hauls up minnow traps and gillnets full of carp, gizzard shad, inexperienced sunfish and, ominously, three smallmouth bass.

“Public enemy primary,” he says as lab technician Justin Furby weighs one on a handheld scale.

Smallmouth bass feast on humpback chub within the river’s higher part. Businesses spend thousands and thousands of {dollars} there yearly to maintain these intruders in examine. The native fish have been safer beneath Glen Canyon Dam as a result of it blocks the trail to the Decrease Colorado and the Grand Canyon, some 200 miles (322 kilometers) downstream — however that is probably not true for lengthy.

Bass up in Lake Powell usually want hotter waters in shallow areas and on the floor. As reservoir ranges drop, they’re 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 aspect.

If massive numbers of bass and different predator fish are sucked into the penstocks, survive and reproduce beneath the dam, they’ll have an open lane to assault chub and different natives, doubtlessly unraveling years of restoration work and upending the Grand Canyon aquatic ecosystem.

That stretch of river is the one place native fish nonetheless dominate the system, mentioned Brian Healy, fisheries biologist for Grand Canyon Nationwide Park. “(It) may be very distinctive and we need to maintain it that means,” he mentioned.

The dam’s completion in 1963 was a main motive the chub practically died out within the river they’d inhabited for thousands and thousands of years. The concrete barrier disrupted water circulate, temperatures and sediments the place the fish spawned. The chub is resilient however hasn’t advanced to resist sudden introduction of predatory sport fish.

Though biologically a minnow, the humpback chub can attain 20 inches (51 centimeters) and a couple of.5 kilos (1.1 kilograms). Silver-sided and white-bellied, with a greenish streak on its again and a particular lump behind its head, it prefers calm eddy waters the place it feeds on bugs.

Its solely predator within the Colorado was one other native, the pikeminnow, till trout had been launched within the early twentieth century to create a sport fishery. Smallmouth bass, much more voracious, arrived within the Nineties.

The chub has gained floor since its itemizing as endangered in 1967, with about 12,000 within the Grand Canyon’s Little Colorado River, a tributary of the Colorado. Scientists estimate 1000’s extra inhabit the primary river farther downstream.

The U.S. Fish and Wildlife Service final 12 months loosened its designation to threatened — now not a step away from extinction, however nonetheless extremely weak. Some environmental teams disagree, calling the transfer untimely because the river’s plunge heightens predation hazard.

As early as this fall, important numbers of bass and different nonnatives may slip out via the dam, mentioned Charles Yackulic, a U.S. Geological Survey statistician who has developed laptop fashions of the risk.

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

The U.S. Bureau of Reclamation, a department of the Division of the Inside which operates the dam, is funding Friesen’s fieldwork underneath Utah State’s Fish Ecology Lab. The group catches fish, notes size and weight, and examines stomachs to see what fish are consuming. Their findings about non-natives close to the dam will assist federal, state and tribal policymakers fine-tune their technique. A technical group advising coverage makers is anticipated to launch a draft plan containing options in August.

One measure into consideration if nonnative predators get via the dam is deploying crews to catch as many as potential. They already do this with brown trout upstream, Yackulic mentioned. Nevertheless it’s costly and never at all times profitable. Native American tribes such because the Pueblo of Zuni take into account the Glen Canyon space sacred and oppose killing fish there, any fish.

“Zuni don’t essentially make distinctions between native and nonnative life kinds,” mentioned Arden Kucate, a tribal councilman. “Sturdy stewardship may be very a lot wanted, a philosophy that acknowledges and treats all nonhuman life kinds as sentient beings.”

Different choices embody penning off areas downstream from the dam the place chub congregate or putting in buildings akin to “bubble curtains” to maintain nonnatives in Lake Powell away from the penstocks.

Or chilly water additionally might be launched from jet tubes deep within the dam to disrupt smallmouth bass spawning downstream, a transfer that has been profitable in different rivers.

“We will use the dam basically as a instrument,” mentioned Clarence Fullard, a Bureau of Reclamation fish biologist.

That transfer, nonetheless, would sacrifice hydropower technology. To handle that, generators might be put in on the jet tubes — however that may require congressional approval. These steps additionally depend upon having sufficient cool water within the river. Ranges at Lake Powell had been comparatively secure for some 15 years, however since 2020, have fallen dramatically.

“The place is the water going to come back from to assist these wanted flows?” mentioned Anne Fort, a senior fellow with the College of Colorado regulation faculty and a former assistant U.S. Inside secretary for water and science.

Wayne Pullan, who oversees the Higher Colorado Basin for the Bureau of Reclamation, declined to take a position, though in recent times, states, tribes and Mexico have taken cuts to their provide, each voluntary and compelled.

“We’re going to depend on these extraordinary relationships and the historical past we have now of cooperation on the river to provide you with options,” Pullan mentioned.

In a worst case situation Lake Powell falls to this point that water would not circulate previous the dam past a trickle, a situation often known as “deadpool.” It could be unlikely within the subsequent few years, however planners needs to be waiting for “a future wherein Lake Powell ceases to exist,” mentioned Taylor McKinnon, senior public lands campaigner with the Heart for Organic Range, an advocacy group.

The prospect is actual sufficient that the Division of Inside is discussing defend native fish if that occurs, Pullan mentioned.

Humpback chub would not be the one victims, McKinnon mentioned. Deadpool additionally would slash Southwest communities’ water provides.

“That may be a sign of our personal self-destruction,” he mentioned.

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Flesher reported from Traverse Metropolis, Michigan.

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The Related Press receives assist from the Walton Household Basis for protection of water and environmental coverage. The AP is solely chargeable for all content material. For all of AP’s environmental protection, go to https://apnews.com/hub/atmosphere

Supply hyperlink
#Biologists #save #historical #fish #Colorado #River #fades

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