Skip Navigation

Species Search:
FieldGuidesthreatened and/or endangered search resultsthreatened and/or endangered


Sea Lamprey Petromyzon marinus


enlarge +

Sea Lamprey, with prey
credit: PDH

All Images


Get Our Newsletters


Advanced Search

Family: Petromyzontidae, Lampreys view all from this family

Description The sea lamprey is very primitive fish resembling fossil records that are over 340 million years old. Unlike most fish, a sea lamprey's body is cylindrical and has cartilage instead of bones. Sea lampreys have no scales, no lateral line, no paired fins and no swim bladder. They have two dorsal fins that are unattached and towards the rear of the body. An ocean lamprey can grow to 1m (3 feet) long and females can weigh up to 2.2 kg (5 lbs) with the males weighing a kilogram lighter.

Dimensions Up to 33" (84 cm).

Habitat Estuaries, tidal flats & salt marshes, Lakes & ponds, Ocean or bay shallows, Open ocean, Rivers & streams, Tidepools.

Range Great Lakes, New England, Mid-Atlantic, Southeast, Florida.

Discussion Adult sea lampreys swim upstream to build nests, spawn and then die. Fertilized eggs hatch into small, wormlike larvae which burrow into stream bottoms where they feed on debris and small plant life (algae) for an average of 3 to 6 years before they transform into the parasitic adult. The adults migrate to open water where they spend 12-20 months feeding on fish. The complete life cycle, from egg to adult, can take an average of 5 to 8 years to complete. Understanding the sea lamprey's life cycle helps scientists develop effective control measures. Lampreys are an invasive species and real problem in the Great Lakes. Sea lampreys were first observed in Lake Ontario in the 1830s. They entered Lake Ontario via man-made canals and then gained access to the upper Great Lakes when the Welland Canal was constructed in 1919. By 1938, sea lampreys could be found in all of the Great Lakes. There are approximately 5,747 streams and tributaries of the Great Lakes and an estimated 433 are currently known to produce sea lampreys.