Scientists’ struggle to save lots of historic fish key to well being of Colorado River

PAGE, Ariz. — 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 US 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 historic fish below assault from nonnative predators within the Colorado River.

The US Bureau of Reclamation fundsFriesen’s fieldwork to assist federal, state and tribal policymakers fine-tune their technique..

The staff notes size and weight of fish and examines stomachs to see what they’re consuming. A draft plan containing options is anticipated to be launched in August.

In this July 7, 2020 image provided by the National Park Service, an adult chub is held on the Colorado River near Shinumo Creek, in Grand Canyon National Park in Arizona.  Low water levels upstream at Lake Powell pose a new risk for the ancient fish.
A Utah State University research team pulls in a gillnet net at Lake Powell on Tuesday, June 7, 2022.
Utah State University master's student Barrett Friesen steers a boat through Lake Powell on June 7, 2022.
Utah State University master's student Barrett Friesen records data about the nonnative fish he is researching for the Bureau of Reclamation on June 7, 2022.

The reservoir’s decline might quickly make issues worse, enabling these nonnative predators 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 filled with carp, gizzard shad, inexperienced sunfish and, ominously, three smallmouth bass.

Smallmouth bass feast on humpback chub within the river’s higher part. Companies spend tens of millions of {dollars} yearly to maintain these intruders in examine. The native fish have been safer under Glen Canyon Dam as a result of it blocks the trail to the Decrease Colorado and the Grand Canyon, some 200 miles downstream – however that might not be true for lengthy.

‘open lane to assault’

Bass up in Lake Powell typically desire 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 facet.

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

Utah State University lab technician Justin Furby weighs a smallmouth bass June 7, 2022. Smallmouth bass feast on humpback chub in the river's upper section, where agencies spend millions of dollars annually to keep the intruders in check.
Utah State University master's student Barrett Friesen steers a boat near Glen Canyon Dam on Lake Powell on June 7, 2022. The dam's completion in 1963 was a primary reason the humpback chub nearly died out in the Colorado River they had inhabited for millions of years.

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 preserve it that manner,” he mentioned.

Dam ‘main cause’ for decline of chub 60 years in the past

The dam’s completion in 1963 was a main cause the chub almost died out within the river they’d inhabited for tens of millions 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 and a pair of.5 kilos. 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.

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