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The National Park Service renewed its efforts to rid an area of the Colorado River in northern Arizona of invasive fish by killing them with a chemical treatment.
A substance lethal to fish but approved by federal environmental regulators called rotenone was disseminated last Aug. 26. It’s the latest tactic in an ongoing struggle to keep non-native smallmouth bass and green sunfish at bay below the Glen Canyon Dam and to protect a threatened native fish, the humpback chub.
The treatment required a weekend closure of the Colorado River slough, a cobble bar area surrounding the backwater where the smallmouth bass were found, and a short stretch up and downstream. Chemical substances were also utilized last year.
The effort would “be carefully planned and conducted to minimize exposure” to humans as well as “desirable fish species,” according to the National Park Service. An “impermeable fabric barrier” was erected at the mouth of the slough to prevent the crossover of water with the river.
Once the treatment is complete, another chemical will be released to dilute the rotenone, the park service said.
Due to climate change and drought, Lake Powell, a key Colorado River reservoir, dropped to historically low levels last year, making it no longer as much of an obstacle to the smallmouth bass. The predatory fish were able to approach the Grand Canyon, where the largest groups of the ancient and rare humpback chub remain.
Environmentalists have accused the federal government of failing to act swiftly. The Center for Biological Diversity pointed to data from the National Park Service released showing the smallmouth bass population more than doubled in the past year. The group also said there still have been no timelines given on modifying the area below the dam.
“I’m afraid this bass population boom portends an entirely avoidable extinction event in the Grand Canyon,” said Taylor McKinnon, the Center’s Southwest director. “Losing the humpback chub’s core population puts the entire species at risk.”
This article was provided by The Associated Press.