The lamprey, an invasive species known for its bloodsucking habits, has become a nightmare for fishermen across the Great Lakes region until scientists discovered an effective compound to eliminate them.
Authorities have declared a rare victory against the bloodsucking invasive fish that nearly collapsed the $7 billion fishing industry in the Great Lakes. Over a century ago, through human activities, the lamprey, a native species of the Atlantic Ocean, invaded the Great Lakes. There, they began voraciously consuming local fish, from salmon to lake trout and walleye, according to National Geographic.
The lamprey threatens the entire fishing industry in the Great Lakes. (Photo: Washington Fish and Wildlife Agency)
“Basically, they just swim in. We opened the door for them when we built the canals,” said Greg McClinchey, policy and legal director of the Great Lakes Fishery Commission (GLFC), an international organization focused on controlling lamprey populations. “We still do not fully understand what this species is capable of.”
A single lamprey can kill over 40 pounds of fish during its larval stage. Each female lamprey lays about 100,000 eggs, with approximately 75% surviving. According to McClinchey, at their peak, they consumed over 100 million pounds of fish, far exceeding human consumption. They also destroyed natural ecosystems more than humans do. Not only were fish in the Great Lakes unprepared to defend themselves against lampreys, but the region also lacked natural predators to help control the invasive species.
A decades-long campaign has helped control the invasive lamprey, marking an unprecedented global victory. The key to success is a new chemical called lampricide, which kills about 90-95% of lampreys in the Great Lakes without harming native species. This campaign has saved the fishery industry in the Great Lakes, according to Marc Gaden, executive secretary of the Great Lakes Fishery Commission.
The lamprey’s predatory mechanism is quite simple. Lacking conventional teeth, they use sharp structures called tooth disks. Lampreys attach themselves to the body of any fish species using these tooth disks, then bore holes into the abdomen of their prey to create open wounds. Their saliva prevents the wound from healing, allowing them to suck blood continuously. As a result, the host experiences significant discomfort. When lampreys began their invasion in the mid-20th century, fishermen complained that when they pulled in their nets, they found so many dead fish that the nets were heavy. Lampreys consume fish five times faster than commercial fishing rates.
In 1954, an agreement among two countries, eight states, one province, and several tribes led to the establishment of the GLFC. Local authorities attempted to control lamprey populations using barriers, electrocution, and even giant sieves, but these methods were ineffective. They needed to find a solution that could eliminate larvae in streams before they transformed into mature fish, swam into lakes, and decimated native fish populations. This led to the lampricide program.
In the 1950s, scientists at the University of Michigan began working with authorities at the Hammond Bay Biological Station on Lake Huron. They explored a chemical that could eliminate invasive fish without affecting native species. After seven years of testing and comparing the mortality rates of native fish and lampreys injected with the same compound, researchers discovered 3-trifluoromethyl-4-nitrophenol, or TFM, a compound that the invasive fish had not evolved to metabolize.
TFM quickly became the backbone of the GLFC’s control program. Many teams were dispatched to distribute TFM in shallow streams where lamprey larvae concentrated before moving to deeper waters as they matured to hunt. The deeper waters remained a refuge for lampreys until the use of niclosamide in the 1990s, a toxin that sinks to the bottom and targets organisms at the riverbed. The program currently maintains the same tactics, combining barrier use to limit the spread of lampreys.
After a long disruption due to COVID-19, treatment operations returned to normal in 2022. The number of lampreys has started to gradually decline. Currently, the GLFC eliminates about 8.5 million lampreys each year. Researchers are also exploring alternative measures, including gene editing and CRISPR technology.
