Great Lakes Fishery Commission

Updated 2023-11-07 19:51:03

Lake Michigan -> 5.0 Sea Lamprey Control -> Lake Trout Wounding Rate

5.1.2 Observed lake trout sea lamprey marking rate below 5 marks per 100 fish

Sea lamprey (Petromyzon marinus) are parasitic fish native to the Atlantic Ocean and were first detected in Lake Michigan in 1936 (Smith and Tibbles 1980). They parasitize and kill other fish by boring a hole into the fish using their rasping tongue and consuming the blood and other body fluids. Sea lamprey control in Lake Michigan began by the end of 1949, when sea lampreys were identified as the reason for the decline in lake trout, with the first attempts at control using mechanical and electrical weirs. Due to the limited effectiveness of these devices, lampricide treatments began in Lake Michigan in 1960 (Lavis et al. 2000). The objective of this control program is to suppress sea lamprey abundance to levels that will not impede achievement of fish community objectives. The sea lamprey population is considered under control if the estimated adult abundance is below 35,000 and the observed lake trout marking rate is below 5 marks per 100 fish.

The marking rate (3-year running average number of A1-A3 marks per 100 lake trout > 532 mm (21 inches)) during the reporting period remained below the control objective, averaging 2.4 marks per 100 fish (Figure 1).

Figure 1. Marking rate (3-year running average of the number of A1-A3 marks per 100 lake trout > 21 inches) from fall assessment surveys and catch monitoring in Lake Michigan, 1981-2021. The control objective is less than 5.0 A1-A3 marks per 100 lake trout.