01-08-2025
Crews deployed to battle invasive 'vampire fish' in Great Lakes
Crews are out in the field, working to keep sea lamprey populations under control this summer, according to a recent social media post from Fisheries and Oceans Canada:
Work began back in April in Lake Erie in Ontario and is expected to continue into October.
That's good news, because when left to multiply, sea lampreys can cause big problems and threaten the Great Lake's $5.1 billion fishing industry.
Yikes! (Canva)
There are four native lamprey species in the Great Lakes - the American brook lamprey, the chestnut lamprey, the silver lamprey, and the northern brook lamprey.
The sea lamprey is invasive, and it can devastate local ecosystems. That has a lot to do with its size. Sea lampreys are big compared to naive species -- up to four times bigger. And in the Great Lakes, they have almost unlimited food availability, practically unlimited spawning grounds, and no natural predators.
Sea lampreys posing for the camera. (Fernando Losada Rodríguez/Wikipedia) CC BY-SA 4.0
COVID-19 restrictions caused a spike in sea lamprey population
COVID-19 safety restrictions paused the ongoing work needed to control sea lamprey populations in the Great Lakes.
A March 2025 study found this caused sea lamprey numbers to "skyrocket," highlighting the need for ongoing control measures.
Experts say the invasive lampreys can kill more fish than humans in the Great Lakes.
Vampire fish
Sea lampreys can inflict gruesome damage on their prey, earning these eel-like parasites the nickname "vampire fish."
Only about one in seven fish attacked by a sea lamprey will survive. They will suction themselves to a fish, creating a seal that's nearly impossible to break off.
They have about 100 teeth, which they use to suction to the side of a fish, and a sharp tongue that drills through its scales.
They secret an enzyme that prevents blood from clotting. Once attached, the sea lamprey will spend the next several months feeding off the blood and fluids of the host animal.
Lake trout with lampreys attached. (Great Lakes Fishery Commission/Wikipedia)
Just in case you're wondering, sea lampreys can accidentally latch on to humans, usually when people are swimming. A bite won't be fatal, but it can be painful, and untreated wounds could lead to infection. Sea lampreys don't pose a threat to people though - they aren't interested in us and human bites appear to be rare.
In their native environment, the Atlantic Ocean, sea lampreys don't often kill their host. In the Great Lakes, where sea lampreys have not co-evolved alongside native species, they are a significant threat.
Shipping canals transport more than just ships
Sea lampreys entered the Great Lakes from the Atlantic Ocean through man-made shipping canals, popping up in Lake Ontario in the 1830s. When the Welland Canal deepened in 1919, sea lampreys gained access to all the Great Lakes -- and they remain there to this day, although their numbers are falling.
In the 1950s, the U.S. and Canada teamed up to implement population control measures), and they have worked.
Several strategies, including traps to capture adult lampreys, lampricides to target sea lamprey larvae, and installing barriers and traps are a few tactics in use.
So far, it's working. Today, sea lamprey populations are down by around 90 per cent in the Great Lakes.
Header image: Cheryl Santa Maria for The Weather Network, using elements from Canva Pro and the public domain.
