The number of invasive, destructive -- and ugly sea -- lamprey is declining in the Great Lakes, according to the Great Lakes Fishery Commission. In Lake Superior, the commission said the 2026 adult sea lamprey index for Lake Superior was estimated at 29,767, a decline from 40,610 in 2025 and less than half the abundance observed in 2023. “Despite the decline, the lake’s three-year average abundance estimate of 41,976 remained substantially above the management target of 10,421,” the commission said in a release. “Biologists completed assessments at all seven index streams. The Bad and Tahquamenon rivers accounted for the largest portions of the lake-wide abundance estimate.” Overall, adult sea lamprey populations declined in four of the five Great Lakes, “reflecting continued progress in the binational effort to suppress populations of this destructive invasive species.” In addition to Lake Superior, lamprey populations declined in lakes Michigan, Huron and Ontario, while Lake Erie experienced a slight increase. “Based on three-year average abundance estimates from 2024 through 2026, sea lamprey populations in Lakes Erie and Ontario remained below established target levels, while populations in Lakes Superior, Michigan and Huron remained above their respective targets,” the commission said. Sea lampreys are invasive, parasitic fish that attack and kill a wide variety of Great Lakes fish species by feeding on their blood and body fluids. For more than 70 years, Canada and the United States have been working to reduce their populations and protect native species. Lampricides, trapping, barriers Sea lamprey control primarily consists of the use of lampricides and barriers, with trapping adult sea lamprey as a means to measure and track abundance. “Sea lamprey control remains one of the Great Lakes’ greatest fisheries management success stories,” Earl Provost, chair of the commission, said in the release. “This year’s results demonstrate that continued investment in control is reducing sea lamprey abundance and protecting fish populations across the basin.” “These achievements are made possible by the dedication, professionalism and expertise of the staff, particularly partners at the U.S. Fish and Wildlife Service and Fisheries and Oceans Canada—who work together across the Canada-US border to carry out this critical work,” Provost added. Control efforts were hampered during the COVID-19 pandemic, when treatments were missed. The impacts are being felt now, since lampreys take years before reaching adulthood and entering the lake from streams. “The good news is that we’ve returned to pre-pandemic levels of control, and the declining abundance we’re seeing in most of the lakes gives us confidence that the program is once again producing the results Great Lakes fisheries depend on,” said Ethan Baker, vice-chair of the commission.
