Great Lakes See Drop in Sea Lamprey Populations
Four of the five Great Lakes recorded lower adult sea lamprey numbers in 2026 compared to prior levels.
Updated on Oct. 20, 2026 in Fishing
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The Great Lakes Fishery Commission reported that sea lamprey populations declined in Lake Huron, Lake Superior, Lake Michigan, and Lake Ontario during 2026. Only Lake Erie saw a slight increase in its adult population index.
Why it matters
Reducing sea lamprey populations is vital for protecting fish stocks, as a single lamprey can kill up to 40 pounds of fish over 18 months. Efforts to control the invasive species were previously disrupted by pandemic-related movement restrictions.
The 2026 abundance indices reached 29,602 for Lake Huron, 29,767 for Lake Superior, 20,211 for Lake Michigan, 7,281 for Lake Ontario, and 923 for Lake Erie. The sea lamprey control program has operated for over 70 years.
The players
Great Lakes Fishery Commission
This binational organization manages the sea lamprey control program and oversees the health of the Great Lakes ecosystem.
The details
Agencies manage the invasive population by using chemical agents called TFM to eliminate larvae in tributaries and conducting capture-recapture surveys to track progress. These programs have historically achieved a 90 per cent reduction in the total sea lamprey population across the basin.
Timeline
2023 saw higher sea lamprey abundance in Lake Superior.
2025 served as the baseline year for annual population counts.
2026 marked the current reporting year for abundance metrics.
Culture Shift
This recovery follows the historical trajectory of the sea lamprey control program, which has faced significant challenges since its inception over 70 years ago. These results highlight the program's resilience in returning to long-term population reduction goals.
The stabilization of these populations protects the regional fish stocks that many anglers rely on for recreational success. Consistent control measures help maintain the ecological health of the waterways frequented by local fishing communities.
The takeaway
Maintaining steady population control is necessary to prevent these invasive parasites from decimating local fish populations. Continued vigilance in tributary monitoring remains the most effective strategy for managing the ecological balance of the Great Lakes.
Further reading
For more background on regional aquatic management, visit the Fishing section.
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Should government prioritize long-term funding for the control of invasive species in national waterways?
