The National Park Service will resume efforts to eradicate invasive fish from a section of the Colorado River in northern Arizona by using a chemical treatment, the agency announced on Friday. Rotenone, a substance toxic to fish but approved by federal environmental regulators, will be distributed beginning on August 26. It’s the most recent strategy in an ongoing battle to keep non-native smallmouth bass and green sunfish at bay below the Glen Canyon Dam and to protect an imperiled native fish, the humpback chub.
The treatment will necessitate the weekend closure of the Colorado River slough, a cobble bar region encircling the backwater where smallmouth bass were discovered, and a brief stretch upstream. Last year, chemical substances were also utilized. According to the National Park Service, the endeavor will be “carefully planned and executed to minimize exposure” to humans and “desirable fish species.” At the entrance of the wetland, a “impermeable fabric barrier” will be erected to prevent water from entering the river.
The park service stated that once the treatment is complete, another chemical will be released to mitigate the rotenone. Smallmouth bass were historically confined to Lake Powell behind the Glen Canyon Dam, which served as a barrier for decades. However, they were discovered in the river below the dam last summer.
Last year, due to climate change and drought, Lake Powell, a critical reservoir on the Colorado River, fell to historically low levels, rendering it less of an obstacle for smallmouth bass. The predatory fish were able to approach the Grand Canyon, where the oldest and rarest populations of humpback chub still exist.
Environmentalists Accuse Federal Government of Delayed Action Amid Surging Bass Population
Environmentalists have charged the federal government with a lack of prompt action. The Center for Biological Diversity cited the National Park Service’s Wednesday publication of data indicating that the smallmouth bass population has more than doubled over the past year. In addition, the group stated that there have been no timelines established for modifying the area below the dam.
Taylor McKinnon, director of the Center’s Southwest region, stated, “I fear this bass population boom portends a completely preventable extinction event in the Grand Canyon.” The loss of the humpback chub’s core population threatens the entire species.
Additionally, environmental organizations continue to criticize the 2021 decision to downlist the humpback minnow from endangered to threatened. The fish, whose name comes from a fleshy protrusion behind its head, was brought back from the verge of extinction after decades of protection, according to federal authorities at the time.
Source: ABC News