Rare, Threatened and Endangered Animal Fact Sheet

American Brook Lamprey

(Lethenteron appendix)

Illustration of American Brook Lamprey, courtesy of  D. A. Neely 

Description & Range:

The American brook lamprey (Lethenteron appendix) is a non-parasitic aquatic species. All lampreys have a long eel-like body and no scales. They have segments of muscles that are visible along their body called myomeres, and a jawless mouth. Taxonomically, it is not considered a true fish because it is so different from other fish species. (True fish have jaws. Lampreys are do not). Unlike the sea lamprey, a relative which latches on to and sucks the blood from other fish with its toothy circular mouth, the adult American brook lamprey doesn’t eat. At all.

The range of the American brook lamprey includes the northeast quarter of the United States, from Minnesota to Arkansas to Virginia and north to the St. Lawrence River. Although secure in most of its range, in the mid-Atlantic region, American brook lamprey populations are declining. In Maryland, it is considered Threatened.

American Brook Lamprey, Courtesy of John Cramer Photography, flickr
American Brook Lamprey (Lethenteron appendix)
Courtesy of John Cramer Photography, flickr


The American brook lamprey is found within slow-moving warm-water streams with forested edges on the Western Shore of the Coastal Plain (south of I-95) in Maryland. This area of the state is under the increasing pressure of urbanization. Loss or degradation of habitat due to development and a lack of mitigation are chief contributors to species decline. Local governments, which determine many zoning laws, can have a huge impact on the state of riparian habitats, and thus have a significant opportunity for conservation. Cooperative participation between MD DNR and local planning agencies is vital if we are to make an effort to conserve the American brook lamprey, and all species of flora and fauna along these waterways.


Adult American brook lampreys do not eat. The lamprey larvae feed on algae up to seven years before metamorphosing into adult American brook lamprey.


Adult American brook lamprey spawn (make a nest in gravel, then lay and fertilize eggs) in late March or early April then will die soon after. The eggs hatch into larvae, called ammoecetes. The lamprey may exist as an ammoecete for up to seven years, feeding on algae, before undergoing metamorphosis into its adult form during late summer. Spawning occurs soon after metamorphosis.

American Brook Lamprey, 
Illustration by D. A. Neely