Great Lakes Fishery Commission

Updated 2026-08-25 14:50:33

Lake Erie-2021-2025 -> 1.0 Intensively Managed Species -> Sea Lamprey Abundance and Wounding Rate

Reduce sea lamprey abundance to levels identified in the sea lamprey management plan

Sea lamprey (Petromyzon marinus) are parasitic fish native to the Atlantic Ocean and were first detected in Lake Erie in 1921 following the deepening of the Welland Canal (Grunder et al. 2020). They parasitize and kill other fish by sucking their blood and other body fluids. They were not considered a serious threat to the Lake Erie fish community until the 1970s when water quality and stream habitat improvements coupled with increased salmonid stocking resulted in the sea lamprey population increasing in abundance. Sea lamprey control in Lake Erie began in 1986 as part of lake trout restoration efforts. The objective of this control program is to suppress sea lamprey abundance to levels that will not impede achievement of fish community objectives, especially for coldwater species. The sea lamprey population is considered under control if the adult abundance is below 3,263 fish and the lake trout wounding rate is below 5 wounds per 100 fish (Slade 2012).

During the 2021-2025 reporting period the average adult sea lamprey abundance index was 2,554 fish, which was below the control objective (Figure 1). The abundance index in 2021, 2024, and 2025 were estimated at 449, 870, and 803 adults, respectively, which were below the control objective and the three lowest index values in the time series. The wounding rate index (average of the number of A1-A3 wounds per 100 lake trout > 532 mm (21 inches)) during the reporting period remained steady but above the control objective, averaging 7.5 wounds per 100 fish (Figure 2). The wounding rate in 2021 and 2022 was estimated at 3.9 and 4.0 wounds per 100 lake trout, respectively, marking the first years below the target wounding rate since 2002.

Figure 1: Index of adult sea lamprey abundance in Lake Erie, 1991-2025. The control objective is less than 3,263 adults.

Figure 2: Wounding rate index (number of A1-A3 wounds per 100 lake trout > 532 mm (21 inches)) from the coldwater assessment survey in Lake Erie, 1985-2025. The control objective is less than 5.0 A1-A3 wounds per 100 lake trout.