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Chippewa River fish kill attributed to lampricide, extreme weather

2023 fish kill in the Chippewa River
2023 fish kill in the Chippewa River

Nearly 70 fish were reported dead by the U.S. Fish and Wildlife Service (USFWS) in the Chippewa River following a chemical treatment that targets invasive sea lampreys.

Fish by kills, or what the USFWS calls “nontarget mortalities," can happen from lampricide treatments, but it’s rare for that number to reach 68 fish.

Jenna Tews, with the USFWS, said warm weather and low river levels resulted in a lower pH, which increased the toxicity of the lampricide.

“We’ve never exceeded maximum levels of toxicity in the treatment," Tews said. "[The nontarget mortality] was associated with some fish species (stone catfish) that are a little more sensitive, coupled with extreme weather temperatures. It’s essentially like treating the river in August.”

Tews said there is no longer any lampricide in the river, and the overall fish population was not impacted by the treatment.

The USFWS conducts a lampricide treatment in the Chippewa River every couple years, targeting approximately 260,000 sea lamprey larvae.

"When it transforms from a larva to an adult and it goes out to Lake Huron to feed, [one sea lamprey] will destroy up to 40 pounds of fish," Tews said. "Certainly, there's a trade-off in conducting sea lamprey control."

Jeremiah Blaauw, with the Michigan Department of Natural Resources, encourages residents to report fish kills.

“We want to do our due diligence to keep those populations healthy and always be mindful of some of the new things that could possibly be coming in [like pathogens and fish diseases],” Blaauw said.

After residents report a fish kill, Blaauw said the DNR will review the submission and may do a site visit to collect and test the fish for possible diseases.

To report fish kills, visit the DNR online reporting system. For more information on lampricide, visit the Great Lakes Fishery Commission website.

Editor's note: In the interest of transparency, the DNR is a financial support of WCMU.

2023 Chippewa River fish kill
2023 Chippewa River fish kill

Teresa Homsi is an environmental reporter and Report for America Corps Member based in northern Michigan for WCMU. She covers rural environmental issues, focused on contamination, conservation, and climate change.