Oneida Lake Education Initiative

"Your gateway to understanding Oneida Lake"

Sea Lamprey

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  • In NY, individuals may reach a length of 24 inches, be as heavy as 0.75 pounds, and may be more than 6 years old
  • Parasitic fish that attaches to other fish and feeds off their bodies
  • Causes large disturbances when landlocked


The sea lamprey is the largest lamprey in the northeast, and is an eel-shaped fish with a skeleton made of cartilage. The most recognizable characteristic of the sea lamprey is its mouth, which looks like a suction cup that is filled with small, but sharp, teeth. Sea lamprey are brown with splotches of dark color on their back and sides, and are a light brown on the belly. They have smooth, scaleless skin and two separate dorsal (back) fins.


Sea lamprey are marine fish that spawn in fresh water, and are found mostly in coastal streams and rivers. However, some populations have become landlocked (no path to the ocean), and are found in lakes during their adult life. These sea lamprey prefer large lakes with reliable streams and muddy bottoms. In New York, landlocked sea lamprey can be found in Lakes Ontario, Erie, Seneca, Cayuga, Oneida, and Champlain. It is a parasitic fish, and primarily feeds on landlocked Atlantic salmon and lake trout. The sea lamprey attaches itself to the prey by using its small teeth and suction-disk mouth. A file-like tongue is then used to puncture the skin and drain the body fluids. This will kill smaller fish, but large fish can survive several attacks.


Sea lamprey spawning usually begins in May when adults migrate into streams. Males arrive first to select a nest site, and build nests by using their sucker mouths to dig a shallow pit. After mating, landlocked females release about 70,000 eggs into the nest, and then both parents die. The eggs hatch in 10-12 days, and the young leave the nest after a week. The first years of life are spent as ammocoetes (am-ah-seats), which are blind, worm-like larvae. These ammocoetes drift from the nest, and plant themselves into soft muddy stream bottoms. After 4-5 years, the ammocoetes transform into the parasitic adult stage and enter the lake. Adults live for 12 to 20 months before entering the spawning cycle.


The sea lamprey belongs to a primitive group of jawless fish called Agnathans. Sea lamprey cause detrimental effects to fisheries and ecosystems, and populations must be controlled by treating spawning rivers with a lampricide that kills the ammocoetes. In the Oneida Lake tributaries, this treatment has been done every 5-7 years since 1984. Sea lamprey has been considered a non-native, invasive species that entered New York during the 1800’s, however, recent genetic studies indicate that the sea lamprey may in fact be native to Lake Champlain.


To learn more about Sea Lamprey ...

Sea Lamprey Factsheet (pdf - 105kb)

Oneida Lake Education Initiative Fish Homepage