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ANN ARBOR — Sea lamprey populations declined in four of the five Great Lakes in 2026, including Lake Michigan, according to new estimates released Monday, Oct. 19, by the Great Lakes Fishery Commission.
Adult sea lamprey abundance decreased in lakes Superior, Michigan, Huron and Ontario, while Lake Erie experienced a slight increase.
In Lake Michigan, the estimated adult sea lamprey population declined to 20,211 in 2026, compared to 21,273 in 2025. The latest estimate was slightly below the lake’s target abundance level of 20,526.
However, Lake Michigan’s three-year average population estimate of 22,094 remained above the target. Adult sea lamprey abundance in Lake Michigan has remained relatively stable and near target levels for much of the past decade.
Sea lampreys are invasive, parasitic fish that attach themselves to other fish and feed on their blood and body fluids. They have been responsible for significant damage to Great Lakes fish populations.
For more than 70 years, the Great Lakes Fishery Commission has coordinated efforts between the United States and Canada to control sea lamprey populations. Control methods include chemical treatments known as lampricides, barriers that prevent lampreys from reaching spawning grounds and trapping programs.
“Sea lamprey control remains one of the Great Lakes’ greatest fisheries management success stories,” said Earl Provost, chairman of the commission. “This year’s results demonstrate that continued investment in control is reducing sea lamprey abundance and protecting fish populations across the basin.”
The commission reported the following adult sea lamprey population estimates for 2026:
- Lake Superior: 29,767, down from 40,610 in 2025. The lake’s three-year average of 41,976 remained substantially above its target of 10,421.
- Lake Michigan: 20,211, down from 21,273 in 2025. The three-year average was 22,094, compared to a target of 20,526.
- Lake Huron: 29,602, down from 44,591 in 2025. The three-year average of 38,026 remained above the target of 31,274.
- Lake Erie: 923, up from 803 in 2025. Despite the increase, the three-year average of 865 remained well below the target of 3,263.
- Lake Ontario: 7,281, down from 11,584 in 2025. The three-year average of 13,747 was slightly below the target of 14,065.
The commission reported that disruptions to sea lamprey control programs during the COVID-19 pandemic continued to affect populations in subsequent years.
“The pandemic created challenges that reverberated through the sea lamprey control program for years afterward,” said Ethan Baker, vice chairman of the commission. “Because sea lampreys spend several years in streams before reaching adulthood, the effects of missed treatments are not immediately reversed.”
Baker said the control program has returned to pre-pandemic levels, with the declining populations indicating that treatments are producing results.
During 2026, control agents assessed 27 of the 29 streams used to estimate adult sea lamprey populations throughout the Great Lakes basin. A total of 29,206 adult sea lampreys were captured at monitoring sites.
Although populations declined in most lakes during 2026, the commission reported that no statistically significant five-year trends were detected in any of the Great Lakes.
The commission continues to evaluate additional control methods while maintaining existing treatment and monitoring programs.
The Great Lakes Fishery Commission was established by the United States and Canada under the 1954 Convention on Great Lakes Fisheries. Its responsibilities include fisheries research, invasive sea lamprey control and coordination of fisheries management between the two countries.
More information is available at www.glfc.org.
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