Sea lamprey numbers dip in Lake Michigan after River treatments

The Great Lakes Fishery Commission reported a slight decline in adult sea lamprey abundance in Lake Michigan, with the 2026 index falling to 20,211 from 21,273 in 2025. This annual estimate places the population just below the management target of 20,526, although the three-year average of 22,094 remains above that threshold.

Control crews completed lampricide treatments on the Pere Marquette River in Mason and Lake counties and Gurney Creek in Mason County this year. The Pere Marquette treatment targeted an estimated 415,305 larvae between July 28 and August 6, while Gurney Creek treatments targeted 1,829 larvae in May.

The commission noted declines in adult sea lamprey abundance in Lakes Superior, Michigan, Huron, and Ontario during 2026. Lake Erie recorded a slight increase, but its three-year average remained well below its management target. Researchers detected no statistically significant five-year trends in any of the Great Lakes despite the annual fluctuations.

Read the full story at shorelinemedia.net.