Northern Brook Lamprey

Northern brook lamprey side view photo with black background
Scientific Name
Ichthyomyzon fossor
Petromyzontidae (lampreys) in the class Agnatha (jawless vertebrates)

All lampreys have snakelike bodies and smooth, slippery skin; a cartilaginous, boneless skeleton; lack an articulating lower jaw; and have a mouth that consists of a rounded sucking disk. There are no paired fins. There are 7 pore-like gill openings along each side of the head.

Unlike parasitic lampreys, brook lampreys (the group of nonparasitic lampreys) don’t have many teeth in their sucking disk, and the teeth they do have are poorly developed, especially near the outer edge of the disk. When expanded, the sucking disk is narrower than the head.

The northern brook lamprey has an undivided though shallowly notched dorsal fin, and all the disk teeth are poorly developed. In the innermost circle, all teeth are 1-pointed. Adults ready to spawn are darkish brown, becoming nearly black by the time spawning is completed.

The larvae (ammocoetes) of all lampreys resemble the adults but lack eyes, and the mouth is a horseshoe-shaped hood instead of a sucking disk. Larvae and new adults are grayish brown above, yellow on the belly and fins.

Similar species: Missouri has six species of lampreys; of these, four are nonparasitic (these are all called brook lampreys; our four species are the southern brook lamprey, northern brook lamprey, least brook lamprey, and American brook lamprey); our other two species of lampreys are parasitic (the chestnut lamprey and silver lamprey).

  • Our four species of nonparasitic brook lampreys are never more than 8 inches long, they have narrow heads, and they have poorly developed disk teeth (the brook lampreys are bottom feeders and do not cling to fish). Missouri's other three brook lampreys are also found in Ozark streams, with the least brook lamprey being much more common than the other two.
  • Our two parasitic lampreys are the chestnut lamprey and the silver lamprey. Both have well-developed, rasplike oral discs with plenty of teeth. The chestnut lamprey occurs in large streams and small rivers of the Mississippi River system, including the lower Missouri River (below St. Joseph) and the larger streams and reservoirs of the Ozarks. The silver lamprey is known only from the Mississippi River, where it is much less common than the chestnut.

Adult length: 6–8 inches long; larvae may grow to nearly 8½ inches long.

Where To Find
image of Northern Brook Lamprey distribution map

Streams in the northern Ozarks, particularly the Osage, Gasconade, and Meramec river systems.

Northern brook lampreys are found in medium-sized streams. They avoid both small headwater creeks and large rivers. All brook lampreys require clear, permanent-flowing streams having clean, gravelly riffles for spawning and stable beds of silt, sand, and organic debris for larval development.

All immature or larval lampreys burrow into soft-bottomed areas of streams and feed on microscopic life and organic particles strained from the water and from the bottom sediments. When lampreys undergo the transformation to adults, they stop feeding and can actually become smaller. Brook lampreys never enter a parasitic stage. When they transform into mature adults in late summer and fall, they remain in their smaller streams without feeding until the following spring, when they spawn.

This is the most common and widely distributed brook lamprey in the northern Ozarks. It may be more widely distributed than records suggest.

Life Cycle

Spawning in Missouri is in early May. Adults excavate pits, carrying stones with their sucker mouths, or spawn between or beneath rocks. Adult lampreys die shortly after spawning. Larval, or ammocoete, lampreys burrow in bottom sediments, using a sieve apparatus to filter microscopic food from the water. The larval stage can last 3–6 years. The transformation to the adult stage takes several months in late summer and fall. As adults, brook lampreys stay in their creeks to spawn and do not eat at all.

Brook lampreys do not parasitize or harm other fish. They are primitive survivors from ancient times, remnants of a group of fishes that lived more than 350 million years ago. They are no more closely related to other living fishes than these fishes are to amphibians and other vertebrates.

Anyone who has owned an aquarium understands the importance of a “bottom feeder.” Brook lampreys eat tiny organisms and other materials and in turn become food for something else. The eggs and the young lampreys, like other small fish, are preyed upon heavily by other fish and animals.

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Similar Species
About Fishes in Missouri
Missouri has more than 200 kinds of fish, more than are found in most neighboring states. Fishes live in water, breathe with gills, and have fins instead of legs. Most are covered with scales. Most fish in Missouri “look” like fish and could never be confused with anything else. True, lampreys and eels have snakelike bodies — but they also have fins and smooth, slimy skin, which snakes do not.