The U.S. National Park Service (NPS) is using chemicals to eradicate invasive bass from the Colorado River flowing through northern Arizona.
According to an announcement from the NPS, they will spray a fish-killing compound approved by the federal environmental agency called rotenone, starting on August 26. This is the latest measure in a persistent effort to stop the smallmouth bass and northern pike below the Glen Canyon Dam and protect the native, threatened species known as the humpback chub. This action requires the closure of a wetland area along the Colorado River for one week. This area surrounds the stagnant water at the riverbank, where smallmouth bass have been detected. Authorities had also previously used chemicals last year.
Invasive smallmouth bass in the Colorado River. (Photo: AP)
The operation will be planned and executed carefully to minimize the amount of chemicals that humans and native fish species are exposed to, the NPS stated. A waterproof barrier will be erected at the wetland’s mouth to prevent water from flowing into the river. After the work is completed, authorities will spray additional chemicals to dilute the rotenone.
Previously, smallmouth bass were isolated in Lake Powell behind the Glen Canyon Dam, serving as a natural barrier for many years. However, last summer, they appeared in the river section below the dam. Due to climate change and drought, Lake Powell, a crucial reservoir of the Colorado River, dropped to a record low last year, failing to prevent the spread of the smallmouth bass. This predatory fish could reach the Grand Canyon, where rare populations of humpback chub still survive.
Environmental experts have condemned the federal government’s slow response. The Center for Biological Diversity cited data from the NPS on August 16 showing that the population of smallmouth bass has more than doubled in the past year. “I fear that this explosion of the bass population foreshadows an extinction event that could have been avoided in the Grand Canyon,” said Taylor McKinnon, director of the center. “The loss of the core population of humpback chub would endanger the entire species.”
Conservation organizations continue to criticize the decision to downgrade the humpback chub from endangered to threatened status by the government in 2021. At that time, federal authorities stated that the humpback chub had recovered from the brink of extinction after decades of protection.
