Great Lakes Fishery Commission

Updated 2023-11-07 19:47:26

Lake Michigan -> 5.0 Sea Lamprey Control -> Sea Lamprey Adult Abundance Index

5.1.1 Sea lamprey estimated adult abundance index below 35,000

Sea lamprey (Petromyzon marinus) are parasitic fish native to the Atlantic Ocean and were first detected in Lake Michigan during 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 most recent average adult sea lamprey abundance index value during the 2016-2021 reporting period was 16,176 (3-year running average), well below the control objective of 35,000 (Figure 1).

Figure 1. Index of adult sea lamprey abundance (3-year running average) in Lake Michigan, 1995-2021. The control objective is less than 35,000 adults.