Chemical treatment to be deployed against invasive fish in Colorado River

PAGE, Ariz. — The Nationwide Park Service will renew efforts to rid an space of the Colorado River in northern Arizona of invasive fish by killing them with a chemical remedy, the company stated Friday.

A substance deadly to fish however authorised by federal environmental regulators known as rotenone can be disseminated beginning Aug. 26. It’s the newest tactic in an ongoing wrestle to maintain non-native smallmouth bass and inexperienced sunfish at bay under the Glen Canyon Dam and to guard a threatened native fish, the humpback chub.

The remedy would require a weekend closure of the Colorado River slough, a cobble bar space surrounding the backwater the place the smallmouth bass had been discovered and a brief stretch up and downstream. Chemical substances had been additionally utilized final yr.

The hassle will “be fastidiously deliberate and performed to reduce publicity” to people in addition to “fascinating fish species,” based on the Nationwide Park Service. An “impermeable cloth barrier” can be erected on the mouth of the slough to stop crossover of water with the river.

As soon as the remedy is full, one other chemical can be launched to dilute the rotenone, the park service stated.

Up to now, smallmouth bass had been sequestered in Lake Powell behind Glen Canyon Dam, which had served as a barrier to them for years. However final summer time, they had been discovered within the river under the dam.

Attributable to local weather change and drought, Lake Powell, a key Colorado River reservoir, dropped to traditionally low ranges final yr, making it now not as a lot of an impediment to the smallmouth bass. The predatory fish had been capable of method the Grand Canyon, the place the biggest teams of the traditional and uncommon humpback chub stay.

Environmentalists have accused the federal authorities of failing to behave swiftly. The Heart for Organic Range pointed to information from the Nationwide Park Service launched Wednesday displaying the smallmouth bass inhabitants greater than doubled up to now yr. The group additionally stated there nonetheless have been no timelines given on modifying the world under the dam.

“I’m afraid this bass inhabitants growth portends a wholly avoidable extinction occasion within the Grand Canyon,” stated Taylor McKinnon, the Heart’s Southwest director. “Shedding the humpback chub’s core inhabitants places your entire species in danger.”

Conservation teams additionally proceed to criticize the 2021 choice to downgrade the humpback chub from endangered to threatened. On the time, federal authorities stated the fish, which will get its identify from a fleshy bump behind its head, had been introduced again from the brink of extinction after a long time of protections.