This small nonparasitic lamprey is one of six species of lampreys native to Ohio. Seldom exceeding seven inches in length they are eagerly sought by stream fishermen in southern Ohio for use as bait and many localized populations have been depleted or eliminated as a result.

Least brook lampreys are primarily found in the smaller high gradient streams in the unglaciated part of Ohio and in those counties fronting the glacial boundary.

They spend most of their lives as ammocoetes (juvenile form) buried in deposits of sand and organic debris where they filter oxygen and nutrients from the water. This aspect of their life history makes them especially sensitive to the effects of siltation as they are easily suffocated.

Many populations have been destroyed by acid mine drainage and siltation from nonpoint runoff. Juvenile lampreys transform into adults during late fall and early winter.

In the spring of the year, usually early April in Ohio, adults move onto gravelly riffles where nests are constructed and spawning occurs. Adults die shortly after spawning and it is only during this short spawning run that their presence in a stream will be detected by the casual observer.