Fish

Lamprey

Petromyzontiformes · also called lamprey eel

Not Evaluated carnivore Rivers & wetlands Coasts & shorelines Ocean

A lamprey has no jaws. It is one of only two surviving lines of the jawless fishes that ruled the seas before jaws were invented, and it still has no bones, no scales, and no paired fins. Its mouth is a round sucker ringed with horny teeth, which the parasitic species clamp onto a fish to rasp through the skin and drink the blood.

Overview

Lampreys are the order Petromyzontiformes, around 45 species, in cool temperate waters of both hemispheres. With the hagfish, they are the only living jawless vertebrates, survivors of a group over 400 million years old. A lamprey has an eel-like body, a cartilage skeleton stiffened by a notochord, and the round toothed sucker mouth.

A long larvae, a short adulthood

A lamprey hatches as a blind, toothless larva, the ammocoete, which burrows into river-bed silt and filter feeds for three to seven years or more, then transforms — growing eyes and the sucker mouth. Adult parasitic species attach to fish and drink blood, kept flowing by an anticoagulant. Many lamprey species never feed as adults at all. All spawn once in gravelly shallows, then die within days, like Pacific salmon.

History and a plague

Lamprey has been a European delicacy since Roman times, and Henry I of England is said to have died in 1135 of “a surfeit of lampreys”. But the sea lamprey, reaching the upper Great Lakes via canals in the early 1900s, collapsed the lake trout fishery and is now held down only by a costly ongoing control programme.

Status

Lampreys as a group are Not Evaluated. The sea lamprey is abundant in its native range and a controlled pest in the Great Lakes, but many freshwater lampreys in Europe and North America are declining, since they need clean gravelly rivers with silt beds for the larvae and clear passage for the spawning run, and dams, pollution, and past eradication have cut their runs.

Lamprey: common questions

Is a lamprey a fish or an eel?

A lamprey is a fish, but a very ancient and unusual kind, and it is not an eel. Eels are bony fish with jaws, fins, and scales. A lamprey has none of those; it belongs to the jawless fishes, an early branch of the vertebrate tree that split off before jaws evolved. The eel-like body is convergence on an efficient shape for moving through water and burrowing. What makes a lamprey a vertebrate at all is that it has a backbone in the broad sense, a nerve cord protected by a series of cartilage elements and the stiffening notochord, along with a distinct head, brain, and paired eyes in the adult.

Do lampreys attack people?

Very rarely, and never fatally. Parasitic lampreys are adapted to latch onto fish, and there are scattered reports of a large sea lamprey attaching briefly to a swimmer, leaving a circular raw mark, usually when the person disturbs a lamprey in shallow water during the spawning run. The lamprey lets go quickly once it realises a human is not a suitable host, and the wound is superficial. Lampreys have no venom, they cannot pursue a person, and the majority of lamprey species do not feed as adults at all. The animal's fearsome-looking mouth is built for holding onto a moving fish, not for biting a large mammal.

Why is the sea lamprey such a problem in the Great Lakes?

Because it arrived somewhere it did not belong and found abundant prey with no defences. Sea lampreys are native to the Atlantic, where fish have evolved alongside them and the lamprey population is limited by the ocean ecosystem. When canal improvements let them past Niagara Falls into the upper Great Lakes in the early 20th century, they encountered large lake trout and whitefish that had never faced a lamprey, and a single lamprey can kill around 18 kilograms of fish in its year or two of feeding. The lamprey population exploded and the trout fishery collapsed. It is now suppressed, at great cost, mainly by applying a chemical that kills lamprey larvae in the streams where they develop, plus barriers and traps.

What are lamprey larvae, and why do they matter?

The larva, called an ammocoete, is so different from the adult that early naturalists classified it as a separate genus. It is a small, worm-like, blind, toothless creature that lives buried tail-down in the fine sediment of stream backwaters for several years, filtering algae and detritus from the water through a mucus net. Ammocoetes are an important part of stream ecosystems, processing organic matter and serving as food for fish and birds, and their long residence means a lamprey population depends on stable, unpolluted, silt-bottomed river reaches. When the larva finally transforms, it rebuilds its whole body, growing eyes and the sucking mouth, in a matter of months.

Sources & further reading

Written by HideShark Editorial Team · reviewed by HideShark Science Desk. Published September 10, 2026. Last updated September 10, 2026.

Quick facts

Scientific name: Petromyzontiformes
Diet: In the parasitic adults, the blood and body fluids of other fish, drawn by clamping the sucker mouth to a fish's flank, rasping through the scales and skin with a toothed tongue, and feeding while an anticoagulant in the saliva keeps the wound open; the burrowed larvae instead filter algae and organic particles from the water, and many lamprey species never feed at all as adults
A vertebrate with no jaws: Lampreys and hagfish are the only living jawless vertebrates, survivors of a group that dominated the seas over 400 million years ago before jawed fish arose, and a lamprey has no true jaws, no bones, no scales, no paired fins, and a skeleton of cartilage and a stiffening rod, the notochord, that runs the length of the body
The mouth is a toothed funnel: An adult parasitic lamprey has a round, jawless disc of a mouth lined with concentric rings of horny teeth and a piston-like tongue also armed with teeth, which it uses to attach to a host and grind an opening, and the arrangement of the teeth is one of the main ways the species are told apart
Years as a blind larva: A lamprey hatches as a small, blind, toothless larva called an ammocoete that burrows tail-first into fine sediment in a stream and lives there filter feeding for three to seven years or more, then undergoes a dramatic metamorphosis, gaining eyes, the sucker mouth, and, in the parasitic species, the drive to migrate
A single reproduction, then death: Adult lampreys stop feeding once they begin the spawning migration, and they build a nest of pebbles in gravelly stream shallows, spawn in groups, and then die within days, having bred only once, in the same pattern as Pacific salmon
A medieval delicacy that killed a king: Lamprey has been a prized food in Europe since Roman times, especially baked in its own blood, and King Henry I of England is traditionally said to have died in 1135 from a surfeit of lampreys, while the City of Gloucester by custom presented a lamprey pie to the British monarch on great occasions
A devastating invader in the Great Lakes: The sea lamprey reached the upper Great Lakes through shipping canals in the early 1900s and, with no natural checks, its parasitism collapsed the lake trout and whitefish fisheries, and it is now held down only by an ongoing multi-million-dollar programme of larvae-killing chemicals, barriers, and traps
Range: The cool temperate waters of both hemispheres, absent from the tropics, with sea-run species spending their adult lives in the North Atlantic, North Pacific, and Southern Ocean coasts and migrating into rivers to spawn, and many wholly freshwater species in the streams, rivers, and lakes of North America, Europe, northern Asia, southeastern Australia, New Zealand, and southern South America.
Conservation status: Not Evaluated ≈ Not assessed as a group of around 45 species, and while the sea lamprey is a controlled pest in the Great Lakes and abundant in its native range, many freshwater lampreys elsewhere are declining or threatened, since they need clean gravelly rivers with silt beds for the larvae and unobstructed passage for the spawning migration, and dams, channelisation, pollution, and past deliberate eradication have reduced runs of the sea, river, and brook lampreys across Europe and North America in the wild