Sea Lamprey Life Cycle

During the spring and early summer, adult sea lampreys ascend streams and rivers to spawn. Male and female sea lampreys seek out riffle areas and construct crescent-shaped nests or redds with small stones and gravel. If large numbers of sea lampreys are spawning in one area, the nests may join and extend between the stream banks. The female may lay 30,000 to 100,000 eggs. After spawning, the adults die.

Most of the fertilized eggs settle in amongst the gravel of the nest and hatch in a few weeks. Eggs that drift downstream may be fed upon by minnows. The young larvae emerge from the nest, drift downstream to a calm area along the stream bank and then burrow into the stream's sand and silt bottom. The larvae feed on algae, detritus, and various small organisms that are filtered from the stream water. After three or more years as a harmless larvae, they undergo a change called transformation.

During this transformation period (late summer and fall), they develop eyes and a sucker-like mouth with sharp teeth and begin to swim downstream to the Great Lakes. After they have entered the Great Lakes, the transformed sea lampreys begin to feed on fish. Each parasitic-phase sea lamprey will spend between 12-18 months in the Great Lakes, destroying an estimated 40 pounds of fish.

Once sea lampreys have reached sexual maturity, they will stop feeding and begin to congregate off the mouths of streams and rivers in preparation for spawning.

 

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