As the Colorado River declines, biologists try to save ancient fish


Arizona Page (AP) — Barrett Friesen steers a motorboat towards the shores of Lake Powell, where Glen Canyon Dam rises overhead. Pale “bathtub rings” line the rocks of the canyon, clearly showing how the water level of the second largest reservoir in the United States has fallen due to increased demand and years of drought. ..

Utah State University graduate students and colleagues are on a mission to save the ancient fish, the Hump Back Chub, which has been beaten by non-native predators on the Colorado River. The decline of the reservoir can quickly exacerbate the situation, and these introduced fish can pass through the dam to reach where the largest group of chubs remain, further downstream of the Grand Canyon. I can do it.

Endangered chubs decades ago have returned in moderation thanks to fish biologists and other scientists and engineers. But in early June, a new threat emerges when Friesen pulls up a minnow trap and gill net packed with carp, gizard shad, green sunfish, and, ominously, three smallmouth bass.

“The number one public enemy,” he says, lab technician Justin Farby weighs one on a portable scale.

Smallmouth bass eat a feast at the Hump Back Chub, upstream of the river. Agencies spend millions of dollars each year to control these intruders. Native fish are safer, but that may not be the case for a long time, as they block the road to lower Colorado and the Grand Canyon about 200 miles (322 km) downstream under the Glen Canyon Dam.

Bass on Lake Powell generally prefers warmer water in shallow areas and on the surface. When the water level in the reservoir drops, it approaches the dam and its penstock. An underwater steel pipe that carries water to a turbine to generate hydroelectric power and discharge it on the other side.

If numerous bass and other predatory fish are sucked into the penstock, survive and breed under the dam, there are open lanes to attack the chubs and other natives, unleashing years of restoration work. This can disrupt the aquatic ecosystem of the Grand Canyon.

Brian Healy, a fishery biologist at the Grand Canyon National Park, states that this river flow is still the only place that dominates the system. “(It) is very unique and we want to keep it that way,” he said.

The completion of the dam in 1963 was the main reason why Chub almost died in a river that had lived for millions of years. Concrete barriers disrupted water flow, temperature, and sediments where fish spawn. Chubs are elastic, but have not evolved to withstand the sudden introduction of predatory sportsfish.

Biologically a minnow, the Hump Back Chub can reach 20 inches (51 centimeters) and 2.5 pounds (1.1 kilograms). It has silvery sides and a white belly, greenish stripes on its back, a distinctive lump on the back of its head, and prefers gentle whirlpool water that feeds on insects.

The only predator in Colorado was another aboriginal, Paiku Minnow, until the early 20th century when trout were introduced to create a sports fishery. An even more greedy smallmouth bass appeared in the 1990s.

Since being designated as an endangered species in 1967, the Chub has been home to approximately 12,000 animals on the Little Colorado River in the Grand Canyon, a tributary of the Colorado River. Scientists estimate that thousands more live in major rivers further downstream.

Last year, the US Department of Fish and Wildlife relaxed its designation as endangered. It’s not a step away from extinction, but it’s still very vulnerable. Some environmental groups disagree, calling the move premature because the plunge in the river increases the risk of predation.

Significant bass and other non-natives could slip through the dam as early as this fall, said Charles Yacklik, a statistician at the U.S. Geological Survey who developed the threatening computer model. ..

Under the Endangered Species Act, government agencies are required to operate in a manner that does not “endanger” the listed animals. This includes infrastructure.

The US Pioneer Department, a branch of the Ministry of Interior that operates the dam, is funding Freesen’s fieldwork under the Institute of Fish Ecology at Utah State University. The team catches the fish, records its length and weight, and examines the stomach to see what the fish are eating. Their findings on non-Indigenous peoples near the dam help federal, state, and tribal policy makers fine-tune their strategies. The technical team, which advises policy makers, will announce a draft plan that includes a solution in August.

One of the measures being considered when non-native predators pass through the dam is to deploy a crew to catch as many predators as possible. They are already doing it in the upstream brown trout, Yackulic said. However, it is expensive and not always successful. Native American tribes, such as Zuni’s Pueblo, consider the Glen Canyon area to be sacred and oppose killing fish there.

“The Zuni do not always distinguish between native and non-native life forms,” ​​said tribal councilor Arden Kucate. “A strong stewardship is very necessary. This is a philosophy that recognizes and treats all non-human beings as sentient beings.”

Other options include penning the area downstream of the dam where the chubs gather, or installing structures such as “bubble curtains” to keep non-natives of Lake Powell away from the penstock.

Alternatively, cold water can be discharged from a jet tube deep inside the dam to confuse smallmouth bass spawning downstream. This is a successful move in other rivers.

“We can essentially use the dam as a tool,” said Clarence Frad, a fish biologist at the Pioneer Department.

But that move will sacrifice hydropower. To address this, the turbine could be installed in a jet tube, but it would require Congressional approval. These steps also depend on whether the river has enough cold water. Lake Powell’s water level has been relatively stable for about 15 years, but has dropped dramatically since 2020.

“Where does water come from to support these necessary streams?” Said Anne Castle of Water and Science, Senior Fellow of the University of Colorado Law School and former US Secretary of the Interior.

Wayne Pulan, who oversees the upper Colorado River for the Pioneer Department, has rejected speculation in recent years, although states, tribes and Mexico have voluntarily and forcibly reduced supply.

“We will rely on those extraordinary relationships and the history we have worked with in the river to come up with solutions,” Pullan said.

In the worst-case scenario, Lake Powell will fall, preventing water from flowing through the dam and beyond the trickle. This is a condition called “deadpool”. It may be unlikely for the next few years, but planners should look to a “future where Lake Powell will disappear,” said a senior public land activist at the biodiversity center of advocacy. One Taylor McKinnon said.

The prospect that the Home Office is discussing ways to protect native fish if that happens is realistic enough, Pullan said.

Hump ​​Back Chubs aren’t the only victims, McKinnon said. Deadpool will also reduce the water supply of the southwestern community.

“It’s a signal of our own self-destruction,” he said.


Flesher reported from Traverse City, Michigan.


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