Lampreys get a bad rap. Their tooth-filled oral disks definitely look scary. Elongate squirmy exoparasites are truly frightening. But here’s the thing: these ancient fishes are ancient survivors that are a key component of freshwater ecosystems. 

Experts disagree, but there are anywhere between 42 and 48 species, all but five found in northern temperate areas. They occur from Alaska to Newfoundland in North America, and Portugal to Siberia in Asia. Although they may look like eels, they are very different from modern bony fishes. These cartilaginous fishes lack jaws, scales, and pectoral and pelvic fins. Most are small, around 15 cm, but one species—the Sea Lamprey—reaches 120 cm in marine environments. Different species can be identified by tooth pattern.  

A cylindrical creature with circular rows of teeth at one end.
The oral disc of a Sea Lamprey collected at the St. Lawrence River at Saint-Vallier, Québec. This is an adult specimen of the seagoing form of Petromyzon marinus. Image: Brian Coad © Canadian Museum of Nature

During their life cycle, lampreys pass through two stages: larval and adult. The larval form—called an ammocoete—burrows in mud and silty areas in rivers and streams. They live there for anywhere between two and 19 years, filtering feeding microbes, detritus and algae. This type of feeding method means that they absorb chemicals and other pollutants from the water. As a result, they have been used to identify exactly what kind of pollution is found in specific rivers. Some species are parasitic as adults, attaching themselves to other fishes to scrape muscle tissue and ingest blood, then grow for a year or more before spawning and dying. Some species don’t even feed as adults; they only live long enough to reproduce once. 

Larval lampreys are important for nutrient recycling in rivers. Their burrowing aerates the river bed. Additionally, ammocoetes are eaten by many types of fish, including White Sturgeon in the Pacific rivers. Lampreys once made up a huge biomass, playing a significant role in the overall ecological integrity of Pacific coastal rivers. One of the most northern colonies of American White Pelicans feeds heavily on adult Arctic Lampreys in Slave River in the Northwest Territories. Seals and sea lions also prey on adult lampreys. Young salmon feed on them when they are very small, while sturgeon consume living and dead adult lampreys. Dead lamprey bodies provide marine-derived nutrients and organic matter to nearby forests through birds and mammals scavenging their carcasses.  

An animal that appears greyish-pink and worm-like with a distinct tail and a slight enlargement of the head.
An ammocoete of the American Brook Lamprey (Lethenteron appendix) from the Richelieu River in southern Québec. This specimen is approximately 7 cm long. Image: Brian Coad © Canadian Museum of Nature
Ammocoetes of Alaskan Brook Lamprey (Lethenteron alaskense), collected by electrofishing from the Martin River in the Northwest Territories. Video: Noel Alfonso © Canadian Museum of Nature

It may surprise you to learn that people have and continue to eat lampreys, particularly in Europe. Baked lamprey pie was a common dish served to the British monarchy. Henry I even died from eating “a surfeit of lampreys.” Many First Nations peoples in the Pacific Northwest ate Pacific Lampreys, whose oil was greatly valued for home use and trade. 

Lampreys are an intriguing group of fishes. They are diverse, are integral components of many ecosystems and have surprising links to humans. Instead of being feared, they deserve some appreciation. 

A number of large pelicans feeding on an eel–like fish.
American White Pelicans feeding on Arctic Lampreys in Slave River. Image: © John David McKinnon