Routine environmental DNA (eDNA) testing for invasive carp found a single positive sample in a Michigan river.
The U.S. Fish and Wildlife Service does annual testing for invasive bighead and silver carp. This year, they found a single positive sample in the St. Joseph River near the St. Joseph/Benton Harbor area.
Only one of the 220 water samples collected in June 2023 from stretches of the river between Lake Michigan and Berrien Springs showed evidence of genetic material from silver carp. That sample was taken near Marina Island.
“A positive eDNA sample does not necessarily indicate the presence of live fish,” said Seth Herbst, DNR Fisheries Research Program manager. “It is possible for genetic material to be introduced from other sources, such as boats or fishing equipment used in another state where invasive carp are present, then transported and used in Michigan waters.”
The sample was taken directly in front of a marina. Officials said this could mean boater traffic could have contributed to the detection.
“We use eDNA results as one piece of information to determine the best response to the potential threat of an invasive species,” said Herbst. “In this case, we have requested assistance from the U.S. Fish and Wildlife Service to conduct another round of eDNA sampling in the St. Joseph River beginning Sept. 5, with results to be processed as soon as possible.”
The USFWS has been conducting monthly electrofishing and netting in the St. Joseph River each summer since 2022 to capture and remove grass carp. They have not caught or spotted any silver carp.
Officials said there is no evidence of any live bighead, silver, or black carp in the Great Lakes or in Michigan Rivers. Anglers are encouraged to learn how to identify invasive bighead and silver carp and report any suspect fish.
“Along with our participation in the eDNA surveillance program, we continue to be diligent with early detection efforts, such as conducting fish population surveys, increasing awareness among anglers, and maintaining an invasive carp reporting website for anglers to share any suspicious catches or observations that occur during their outings,” said Herbst.
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