What is a sea lamprey?
It’s a jawless, primitive, eel-like fish. Yes, it’s a fish.

Where do they come from and where do they live?
Sea lampreys originated in the Atlantic Ocean but early in the 20th century they made their way to the Great Lakes through shipping canals. Sea lampreys are aggressive predators and are not native to the Great Lakes. They are considered an aquatic nuisance species (ANS for short). This means they are not native to these waters and they do much damage--they are not welcome! Sea lampreys are anadromous and live most of their lives in the gravel beds of streams for 4 to 7 years and as long as 14 years and grow to as large as three feet.

What is anadromous (ana-dro-mus)?
It’s when a fish species can live in either fresh water or saltwater. It swims from open water (like the Great Lakes) to smaller streams and tributaries of the lakes. When they swim upstream, they spawn and produce more lampreys.
How are they harmful?
Sea lampreys are parasitic. This means they attach, live and feed off of other fish in order to survive. Adult sea lampreys feed off of lake trout (and other fish) by attaching to the side of the fish (called a host) like a vacumm cleaner. Once attached, it uses its sharp rows of teeth and rasping tongue to live off of the fish. Even when the sea lamprey is knocked off or leaves its host fish, the fish often dies from the damaging wound left behind.

So then lampreys are bad, right?
Not all lampreys are parasitic. Species classified as brook lampreys are non-parasitic and can even be endangered species. Lampreys in some states are used as bait and in some countries considered “a delicious meal.”

What is being done to help the fishes (fishery)?
After many years of research, biologists are winning the battle against the “attack of the sea lampreys.” While the sea lampreys are in the streams, a lampricide is released into the water. It attracts and kills the sea lampreys before they can reach open water. With the exception of some catfish, this chemical control does not affect other fish species. This chemical weapon along with water barriers at the mouths of streams, traps and electric shocks have reduced the sea lamprey population by 90% in the Great Lakes.