Hello,

Your inquiry was sent to me via the Ask an Expert website.  From the pictures, and with my fairly limited experience identifying fish parasites, I cannot say for certain if these fin parasites are copepods, or if they are native to the Great Lakes.  I suggest you email the pictures to Steve Stewart and Andrew Briggs, who are closer to the St. Clair River and may have heard from other anglers reporting the same parasites.  I am stationed in west Michigan and deal mostly with Lake Michigan in recent years.

Steve Stewart, MSU Extension in Southeast Michigan

Andrew Briggs, Michigan DNR Fisheries Research Biologist at Lake St. Clair Fisheries Research Station

Hope this helps,  and please copy me on any continued email correspondence with Steve and Andrew. 

Dan O'Keefe

MSU Extension & Michigan Sea Grant

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