Sea lamprey numbers fall in four of five Great Lakes in 2026

Control crews are making headway against the Great Lakes' blood-feeding invader. The Great Lakes Fishery Commission reports that adult sea lamprey abundance fell in Lakes Superior, Michigan, Huron and Ontario in 2026, while Lake Erie edged up slightly. Officials credit a return to full, pre-pandemic treatment levels. Because lampreys spend years in streams as larvae, the treatments missed during the pandemic took several years to show up in adult counts.

Lake Superior's index dropped to about 29,800 from 40,600 in 2025, but its three-year average of nearly 42,000 is still far above the target of about 10,400. Lake Huron fell to about 29,600 from 44,600 and remains above target on a three-year basis. Lake Michigan held near its target at about 20,200.

Lake Erie rose to 923 from 803 but is still well under its target. Lake Ontario fell to about 7,300 from 11,600, putting its three-year average just below target.

Crews assessed 27 of 29 index streams and caught 29,206 adult lampreys basin-wide. The Commission noted that no lake showed a significant five-year trend. It says continued lampricide treatments, barriers and monitoring, carried out with the U.S. Fish and Wildlife Service and Fisheries and Oceans Canada, are what protect lake trout, whitefish, salmon and walleye from lamprey attacks.

This is a The Gillnet news desk summary, not a reprint.

Source: Great Lakes Fishery Commission — Sea Lamprey Populations Decline Across Most Great Lakes in 2026 (Oct. 19, 2026).