Swimming deep inside the Great Lakes with 150 teeth, a serrated tongue, and a ruthless hunger, this ‘vampire’ could destroy the entire ecosystem

The invasive sea lamprey, often dubbed “vampire fish" for its bloodsucking predation, has prompted Canadian and US agencies to launch a joint campaign to protect the Great Lakes' $5.1-billion freshwater fishery.

Control crews initiated treatments in late April, focusing on Lake Erie and Lake Ontario, with operations expected to continue through October.

The methods employed include lampricides (chemical treatments), traps, and barriers aimed at reducing the sea lamprey population, which parasitically feeds on fish.

What are sea lampreys?

Sea lampreys, native to the Atlantic Ocean, were inadvertently introduced into the Great Lakes via shipping canals in 1921. Lacking natural predators in this new environment, they have wreaked havoc on native fish populations. Using their mouths, equipped with 150 teeth and a serrated tongue, they latch onto prey, often killing up to 40 pounds of fish during their parasitic stage.

The COVID-19 pandemic exacerbated the issue. Travel restrictions in 2020 and 2021 forced crews to pause treatments, allowing millions of lamprey larvae to survive.

A new study confirms that lamprey numbers rose sharply during this period. In 2024, adult sea lamprey counts were 8,619 above pre-COVID-19 averages, with Lake Superior and Lake Ontario experiencing the most significant increases.

Ethan Baker, chair of the Great Lakes Fishery Commission, emphasized the urgency:

“Ongoing, consistent sea lamprey control is critically important for preventing damage to Great Lakes fish by invasive sea lampreys. If we take our foot off the gas, even for a short while, sea lamprey populations will increase rapidly and cause considerable damage to fish.”

The Great Lakes Fishery Commission, established in 1955, has been instrumental in reducing sea lamprey populations by 90 percent in most areas of the Great Lakes. Their integrated control program combines several methods to attack sea lampreys on multiple fronts.

The primary method involves applying the lampricide TFM to target sea lamprey larvae in their nursery tributaries. In the concentrations used, TFM kills larvae before they develop lethal mouths and migrate to the lakes to feed on fish, while most other organisms are unaffected.

The ‘Trump’ factor

The Trump administration's mass purge of federal workers, including 12 members of the Great Lakes sea lamprey control program, has raised concerns about the program's efficacy. These staffing cuts represent nearly 14 percent of the lamprey control program’s overall workforce, potentially allowing over 1 million lamprey to survive, consuming nearly 5 million pounds of fish and resulting in $105 million in lost economic output.

Despite these setbacks, control efforts have resumed. Scientists and officials warn that the damage done during the pause will take years to reverse.

The Great Lakes Fishery Commission continues to stress the importance of sustained efforts to safeguard the prosperity of the region.