The Resurgence of Sea Lampreys in the Great Lakes
The COVID-19 pandemic has brought about unexpected consequences in various aspects of life, including the environment. Fisheries officials in the Great Lakes have recently discovered a troubling resurgence in the population of sea lampreys, a notorious threat to commercial fisheries in the region. This resurgence serves as a stark reminder of the ongoing challenges in combating established invasive species, even after years of dedicated efforts.
Since the introduction of oceangoing shipping to the Great Lakes, the freshwater ecosystem has been plagued by invasive species from around the world, with the sea lamprey being one of the most destructive. Originally native to the North Atlantic, sea lampreys found their way into the Great Lakes through the Welland Canal in the late 19th century. With the ability of a female lamprey to produce up to 100,000 eggs per year and the absence of natural predators in the lakes, the population of these parasitic fish quickly spread throughout the entire system.
The impact of sea lampreys on the commercial fisheries in the Great Lakes was devastating. Unlike in their native habitat where they typically do not kill their host fish, in the Great Lakes, each lamprey can consume up to 40 pounds of fish annually, leading to a drastic decline in the population of native species like lake trout. The commercial catch of lake trout plummeted by 98 percent between the 1920s and early 1960s due to lamprey predation.
In response to this crisis, Canadian and American fishery officials joined forces to establish the Great Lakes Fishery Commission, a bilateral agency dedicated to finding solutions to the lamprey problem. Through years of research, the commission developed targeted control measures, including the use of a chemical compound that is lethal to lamprey larvae but minimally harmful to other species. This approach proved to be highly successful, reducing lamprey populations by over 90 percent over six decades.
However, the COVID-19 pandemic disrupted the lamprey control program, leading to a decrease in control measures in 2020-2021. As a result, lamprey populations began to rebound, surpassing target levels in all of the Great Lakes by 2024. The Great Lakes Fishery Commission anticipates that it will take until 2025-2026 for lamprey populations to return to desired levels, underscoring the need for continuous management of this invasive species.
Jim McKane, the Commission’s vice-chair, emphasized the importance of consistent lamprey control efforts, stating, “After more than six decades of successful sea lamprey control, the reduced effort during the COVID-19 pandemic shows that if controls are ceased or relaxed for even a short period of time, sea lamprey populations will rebound, and the fishery will suffer.”