Great Lakes Fishery Commission

Updated 2024-12-06 15:25:31

Lake Huron -> 9.0 Sea Lamprey -> Lake Trout Wounding Rate

9.2. Marking rate on lake trout (3-year average) < 5 marks per100 Lake Trout

Sea lamprey (Petromyzon marinus) are parasitic fish native to the Atlantic Ocean and were first observed in Lake Huron in 1937 (Applegate, 1950). They parasitize and kill other fish by sucking their blood and other body fluid, and contributed to the decline of commercial Lake Huron fish populations (Nowicki et al. 2021). The objective of the control program is to reduce sea lamprey abundance to levels that will allow the achievement of other fish-community objectives. The sea lamprey is considered controlled when the 3-year average adult abundance is below 31,274 and the 3-year average lake trout marking rate is below 5 A1-A3 marks per 100 large lake trout (>532mm (21 inches)).

The sea lamprey adult abundance index remained above the control target during the reporting period (2018-2022). The trend is downward, however, as the mean decreased from approximately 66,000 during the previous reporting period (2011-2017) to 44,000 during this reporting period (2018-2022). The index increased slightly in 2020 and 2022, but still remained lower than all years prior to 2014.

The sea lamprey marking rate on lake trout ranged from 4.7 to 7.5 during 2018-2022. The 3-year mean in 2022 met the target and was the lowest in the entire time series. The trend is downward because the mean marking rates in the previous reporting period (2011-2017) were approximately 9 marks per 100 fish, and decreased to approximately 6 in 2018-2022.

The St. Marys River was the largest sea lamprey producing stream in the Great Lakes prior to sea lamprey control efforts in the river and was the largest contributor of sea lampreys to northern Lake Huron.  Two control methods used in the river included sterile male release technique (SMRT) and lampricide control using the formulation of granular Bayluscide. Since 2012, SMRT was removed as a control method and only lampricide treatments of over 300 hectares of high-density areas of larval sea lampreys are treated annually.

Annual number of A1-A3 sea lamprey marks per 100 adult large Lake Trout (three-year moving average) in Lake Huron, 1987-2022. The three-year average for sea lamprey spawning years 2020-2022 (4.6) met the control target (5.0).