Head to head
Sea Lamprey vs European Eel
A lamprey and an eel are both long, slippery, and snake-shaped, and both spend part of their lives in rivers and part at sea. That is where the similarity ends. The eel is an ordinary bony fish that happens to have a long body. The lamprey belongs to one of the two surviving lineages of jawless fish, a group far older than any fish with jaws, and it makes its living by attaching to other animals and feeding on them.
| Sea Lamprey | European Eel | |
|---|---|---|
| Jaws | None; a round rasping sucker mouth | Yes, an ordinary fish jaw |
| Skeleton | Cartilage and a notochord; no true bone | Bony, with a full backbone |
| Paired fins | None | Pectoral fins present |
| Gills | Seven open gill pores behind each eye | One gill cover on each side, like other fish |
| Feeding as an adult | Parasite: attaches to fish and rasps in to feed on blood | Predator of invertebrates, fish, and amphibians |
| Migration | Anadromous: grows at sea, breeds in rivers, then dies | Catadromous: grows in rivers, breeds in the Sargasso Sea, then dies |
| Larva | Ammocoete, blind and burrowing, filter-feeds for years | Leptocephalus, transparent and leaf-shaped, drifts on currents |
| Status | Native and declining in Europe; invasive in the North American Great Lakes | Critically Endangered |
Lamprey vs Eel: common questions
Is a lamprey a kind of eel?
No, and they are not even close relatives. An eel is a bony fish, a member of the huge group of ray-finned fishes that also contains cod, tuna, and goldfish; it simply has an elongated body. A lamprey is a jawless fish, one of only two surviving groups, along with the hagfish, from a stage of vertebrate evolution that predates the origin of jaws by tens of millions of years. A lamprey has no jaws, no paired fins, no bone, and a fundamentally different body plan. The resemblance to an eel is pure convergence, both being long and limbless because that shape works for moving through water and burrows.
Do lampreys attack people?
Very rarely, and not seriously. A sea lamprey feeds on fish, and its sucker mouth and rasping tongue are built to grip a slippery, scaled fish and grind through its skin. There are occasional reports of lampreys attaching briefly to swimmers, usually in cold water where the lamprey may be seeking any large warm object, and the result is a temporary circular sucker mark and, at worst, a shallow graze. A lamprey cannot do meaningful harm to a person and is not interested in one as food. The animal it is genuinely dangerous to is a lake trout or a whitefish, which can be killed by the wound and the blood loss.
Why is the eel Critically Endangered while the lamprey is a Great Lakes pest?
Different stories in different places. The European eel has collapsed, with the number of young eels arriving in Europe down by around 90 to 95 per cent since the 1980s, because of dams and hydropower turbines blocking and killing migrating fish, habitat loss, a parasite that damages the swim bladder, pollution, changing ocean currents affecting the larval drift, and an enormous illegal trade in baby eels, or glass eels, smuggled to Asian farms. The sea lamprey is native to the Atlantic and is also of conservation concern in parts of Europe, but in the North American Great Lakes it is an invader that entered through shipping canals in the twentieth century, had no natural controls, and devastated the lake trout fishery, so there it is the target of a large, permanent control programme using selective poisons and barriers.