Lamprey: The Parasites of The Great Lakes

For many, the word parasite evokes a rather specific image: a small, crawly creature that burrows and feeds off unsuspecting hosts. And, while organisms like these do exist, they are a remote worry in daily life. Truly, many parasites aren’t as scary as popular media leads one to believe. Parasites often don’t even fit into the strict and distinct characteristics that govern other animal groups such as mammals or amphibians. Yet, they all have one thing in common, one thing that defines, shapes, and guides their entire existence: their inability to live without a host. 

Eel-like leeches

Similar to Leeches, the infamous aquatic parasite, Lamprey feed on the blood and other bodily fluids of their prey.

Despite their classification as a fish, these marine parasites lack bones and therefore belong to the order of Agnatha, or jawless fish. Their bodies of cartilage allow their jaws to open enough to latch onto their hosts with horn-like teeth. They are often considered eel-like in appearance, shape, and size.

Eating habits and methods

Once latched onto their host, their rough tongue wears away at the host’s skin to feed on its blood and other fluids. A single invasive Lamprey can kill up to 40 pounds of fish in its life with a 40-60% mortality rate. While they prefer to feed on the blood and fluids of salmon and trout, they have also been found to feed on walleye, pike, and sturgeon.

Effects of an invasive parasite

As one can imagine, these parasites can quickly become unhealthy for the ecosystem, especially when they become invasive. After the creation of shipping routes from the Atlantic Ocean to the Great Lakes in the 1800s, the Lamprey invaded, soon killing wildlife and hunting native trout to near extinction in all lakes except Lake Superior. Contained in the lower lakes due to the natural barrier of Niagara falls, they also wreaked devastation on New York's sturgeon, which are now labeled an endangered species, largely as a result of the parasites. 

Additionally, fisheries around the Great Lakes began to fail due to the overwhelming Lamprey populations’ high mortality rates. This led to a substantial loss of profit to local economies, jobs, and food for local communities and resulted in action from Canadian and US governments to put an end to the invasion. 

Lampricides

Today, Lamprey populations in the Great Lakes have fallen by 90% due to increased efforts to  research and control Lamprey populations that threaten national fisheries. In the 1950s, scientists discovered TFM (3-trifluoromethyl-4'-nitrophenol) and Bayluscide (2', 5-dichloro-4'-nitro salicylanilide), two compounds that target young Lamprey while leaving the environment unharmed.

Lovingly nicknamed Lamprocides, these two compounds work hand in hand to ‘treat’ rivers, tributaries, and lakes every three to five years. While not completely eradicated from the environment, TFM and Bayluscides keep Lamprey under control and ensure native populations survive and rebound from the invasive parasites. 

While the vampires of the Great Lakes are elusive, deadly, and worrisome to marine scientists, they have yet to escape the clutches of chemicals. No longer are they a looming threat to fragile marine ecosystems and local communities relying on tourism and fishing industries. Yet, unfortunately for scientists, it’s highly unlikely for Lampreys to completely disappear from the water due to their uncanny ability to invade, take over, and thrive in alien environments. 

References

Great Lakes Fishery Commission. SEA LAMPREY. A Great Lakes Invader. 2000, https://www.glfc.org/pubs/FACT_3.pdf.

“Great Lakes Invasives: Sea Lampreys.” Shedd Aquarium, 3 March 2020, https://www.sheddaquarium.org/stories/great-lakes-invasives-sea-lampreys. Accessed 11 November 2024.

Kraker, Dan. “'Vampire of the Great Lakes' still haunts Lake Superior fish.” MPR News, 31 October 2017, https://www.mprnews.org/story/2017/10/31/invasive-sea-lamprey-lake-superior-rebound. Accessed 11 November 2024.

“Lampricide.” Great Lakes Fishery Commission, https://www.glfc.org/lampricide.php. Accessed 12 November 2024.

Lohan, Katrina. “Marine Parasites: Crazy…and Really Cool! | Smithsonian Ocean.” Smithsonian Ocean, https://ocean.si.edu/ocean-life/invertebrates/marine-parasites-crazyand-really-cool. Accessed 2 November 2024.

“Marine Parasites Are Creative Masterminds.” Ocean Conservancy, 17 June 2020, https://oceanconservancy.org/blog/2020/06/17/marine-parasites/. Accessed 11 November 2024.

“Meet the invasive 'vampire fish' that lives in the Great Lakes.” The Weather Network, 11 March 2022, https://www.theweathernetwork.com/en/news/nature/animals/meet-the-invasive-vampire-fish-that-lives-in-the-great-lakes-sea-lamprey. Accessed 14 November 2024.

“Pulse on Science: Project Spotlight.” Great Lakes Fishery Commission, https://www.glfc.org/pulse-on-science-polymer-packages.php. Accessed 14 November 2024.

“Sea Lamprey - NYSDEC.” New York State Department of Environmental Conservation, https://dec.ny.gov/nature/animals-fish-plants/sea-lamprey. Accessed 11 November 2024.

“Sea Lamprey – Profile and Resources.” Invasive Species Centre, https://www.invasivespeciescentre.ca/invasive-species/meet-the-species/fish-and-invertebrates/sea-lamprey/. Accessed 14 November 2024.

“What is a sea lamprey?” National Ocean Service, 16 June 2024, https://oceanservice.noaa.gov/facts/sea-lamprey.html. Accessed 11 November 2024.