Britannica
Sources used in this answer
Why do many adult lampreys migrate from the sea into freshwater streams?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
agnathan
Lamprey (Lampetra) on rainbow trout.
Adult lampreys migrate from the sea into freshwater streams primarily to spawn. These diadromous fish return to freshwater environmentsâspecifically those characterized by strong currentsâto build nests in gravel or sand beds.12
During this process, they locate suitable spawning grounds by following pheromones released by either males or larval lampreys. Once they have successfully spawned, the adults die, as the reproductive process takes a significant toll on their digestive systems. The resulting eggs hatch into larvae that remain in the freshwater stream beds for several years before undergoing metamorphosis and eventually migrating back to the sea.21