An Overview of Invasive Species
The Great Lakes are home to numerous invasive species, including zebra and quagga mussels, round gobies, alewives, spiny water fleas, and sea lampreys. Sea lampreys, ancient creatures that predate dinosaurs, were first discovered in Lake Ontario in 1835 and had migrated to Lake Superior by 1946. These aggressive fish can grow up to two feet long and lack natural predators, leaving other fish defenseless against them.
The Destructive Impact of Sea Lampreys
Lampreys attach to fish with their suction cup mouths and use a rasping tongue to cut into their victims, extracting bodily fluids and blood. Each attack leaves behind 46 different parasites, bacteria, and fungi. Over their 18-month feeding period, a single lamprey can kill up to 40 pounds of fish in the Great Lakes. Once established, their population exploded, devastating fish populations. By the 1950s, sea lampreys were responsible for killing 100 million pounds of fish annually, with 85 percent of survivors bearing attack wounds.
A Breakthrough in Control: TFM
In 1954, US and Canadian officials convened to devise a strategy to halt the lamprey invasion. Scientists, in a desperate search for a solution, tested nearly 6,000 chemical compounds before developing a lampricide called TFM (3-trifluoromethyl-4-nitrophenol). Discovered and field-tested in 1957, TFM was put into general use in 1958.
Sea lampreys migrate upstream to spawn in the warm, shallow tributaries of the lakes. Each female can lay up to 100,000 eggs per season. After hatching, the larvae drift downstream to silty areas, where they burrow into the mud and grow for up to ten years before emerging. It is during this vulnerable larval stage that TFM is effective, attacking their metabolism and leading to their demise.
Decades of Successful Management and Ongoing Vigilance
Annually, employees and seasonal hires spread TFM in the tributaries, eliminating over five million larvae. Thanks to decades of lamprey management, the sea lamprey population in the Great Lakes has been reduced by 90 percent compared to the late 1950s. Consequently, fish mortality attributed to lampreys has decreased to approximately 10 million pounds annually. This cooperative effort stands as the most successful aquatic invasive species control program in American and Canadian history.
The story of lampreys in the Great Lakes serves as a cautionary tale regarding the potential devastation caused by invasive species. While control efforts have significantly reduced the lampreys’ impact, ongoing vigilance remains crucial. Continued monitoring, research, and adaptive strategies are essential to ensure these creatures do not resurface to threaten the health and stability of the Great Lakes ecosystem. This past spring, the program experienced an arbitrary one-third reduction in funding, but a bipartisan outcry six weeks later led to its restoration to full strength. Program continuity requires constant vigilance.
A note on taste: you might wonder what sea lamprey tastes like? Don’t order them at your local sushi bar. They are not going to replace Colonel Sanders’ chickens any time soon.
Research by Jim Hubbell
Special thanks to Jim Hubbell of the Illinois Region for researching this story.
Learn more about sea lampreys in Lake Michigan in this video from the Milwaukee County Historical Society.