This page copied from:
U.S. Fish and Wildlife Service Connecticut River Coordinator's Office
Restoring Migratory Fish to the Connecticut River Basin


The sea lamprey (Petromyzon marinus) is a snake-like fish that is often under-appreciated. However, it is an important, non-parasitic native in the Connecticut River (see Life History). The lamprey is often confused with eels, but its jaw-less, circular sucking disk helps to distinguish it from the American eel, which has a true jaw. Adult lampreys are mottled brown above and lighter below, with lighter areas becoming bright yellow during the spawning season. Adults average 24 to 30 inches in length.

Life History

The sea lamprey is anadromous (migrating from the ocean to freshwater specifically to reproduce). When they enter the Connecticut River to spawn, they stop feeding, so they are not a threat to inland fishes (as they are in other areas, such as the Great Lakes). All of their reserve energy is saved for spawning, which occurs in the spring. Upon depositing the eggs and milt (sperm) in a stony nest, the adults die. The unattended eggs hatch about two weeks later. Larvae drift downstream, eventually burrowing into a sandy or silty area. The young lamprey remain in freshwater for up to 10 years, when they migrate to the ocean. It is in the ocean that lamprey become parasitic. They use their sucking disks lined with rows of teeth to extract body fluids from a host fish. Their ocean phase lasts one to two years.


The sea lamprey is widely distributed along the coasts of eastern North America and Europe. Landlocked populations also exist in some inland water bodies such as the Great Lakes and Lake Champlain. In the Connecticut River basin, sea lamprey enter the larger tributaries, and are documented as far north as Bellows Falls Dam (175 miles from the mouth).


The Connecticut River sea lamprey population appears to be relatively stable. For the last 20 years, lamprey counts at the Holyoke Dam have averaged about 30,000 per year. Sea lamprey are a unique, natural part of the Connecticut River ecosystem, and the larvae are an important food source for other fishes. In contrast, populations accidentally introduced to landlocked areas (such as the Great Lakes and Lake Champlain) become parasitic in fresh water and have done great damage to native fisheries in these systems. In such areas, State and Federal agencies carry out active control programs in an effort to protect fish diversity.

Restoration Efforts

Though sea lamprey have benefited from fish passage facilities in the Connecticut River watershed, there are no current programs specifically designed to increase sea lamprey populations.