Distinguished from the other native lamprey by its silvery color, continuous dorsal fin, and unicuspid teeth. Generally distributed along the Great Lakes and in the large tributaries of the Mississippi and Ohio Rivers from Minnesota to Nebraska, Tennessee, and West Virginia. Isolated records from the Hudson Bay drainage and from the Mississippi River in the State of Mississippi.
Parasitic adults live in larger streams and lakes where they find their fish hosts.
Larval ammocoetes require sand and dark mud, relatively free of clay silt. Adults parasitic upon other fishes, attaching to host with suction-cup mouth. Sharp teeth cut through skin and scales and the blood is extracted. Remains attached to host over a long period of time unless brushed off by the distressed fish. Fishes almost colorless from the loss of blood have been observed with several lampreys attached, but they seldom kill the host since that would deprive them of their food source.