
Local rivers treated as sea lamprey numbers decline in Lake Michigan - Shoreline Media Group
Sea lamprey control crews completed treatments on the Pere Marquette River in Mason and Lake counties and Gurney Creek in Mason County this year, as the Great Lakes Fishery Commission reported a slight decline in Lake Michigan’s adult sea lamprey abundance. The Pere Marquette River treatment targeted an estimated 415,305 larvae during a July 28-Aug. 6 treatment window. Gurney Creek’s treatment targeted an estimated 1,829 larvae during a May 5-14 window. Both are listed as completed on the commission’s treatment schedule, updated Sept. 23. Those figures represent estimates of larvae targeted, rather than confirmed numbers killed. Treatments use lampricides to control larvae before they mature and move into the Great Lakes. Lake Michigan’s adult sea lamprey index fell to 20,211 in 2026 from 21,273 in 2025, putting the annual estimate just below the management target of 20,526. However, its three-year average of 22,094 remained above that target, according to the commission. The local treatments are part of an ongoing effort between the United States and Canada to suppress the invasive parasitic fish, which attack Great Lakes fish by feeding on their blood and body fluids.












