River Lamprey

The river lamprey (Lampetra ayresii) is a member of the family Petromyzontidae, found in rivers from Alaska to California. This species can occupy a variety of habitats, including marine surface waters as well as freshwater lakes, rivers, and creeks, depending on its life stage. They lack scales and true jaw, and instead have a flat, circular mouth structure called an oral disc. River lampreys are dark brown along their dorsal, lateral, and tail regions, with yellow coloring on the ventral side and silver coloration sometimes around their head. Adult river lamprey typically reach a total length of approximately 17 to 18 cm. River lamprey leave freshwater habitats in late spring to early summer to feed in marine environments before returning to rivers in the fall. Larval river lamprey burrow into soft streambed substrates, where they feed on microscopic plants and animals until undergoing metamorphosis at around 9 to 10 months and migrating to the ocean. As parasitic adults, they suction to other fish with their oral discs, and feed on muscle tissue. River lamprey return to freshwater streams to spawn, with an estimated 11,400 to 37,300 eggs laid per female.

Fun Fact: The river lamprey has a reduced number of teeth compared to other lamprey species, allowing it to reposition its feeding site on prey more easily.