Salmon and other migratory fish use olfactory imprinting as juveniles to memorize the chemical signature of their natal stream for return migration.
Fish that fail to return to appropriate spawning habitat due to disrupted olfactory navigation or physical barriers cannot fulfill their biological drive to reproduce. The physiological changes of spawning condition that cannot be resolved through reproduction represent a form of biological frustration. River restoration that maintains both chemical integrity and physical access enables successful spawning migrations and the welfare of reproductive fulfillment.