Migratory fish including salmon use olfactory imprinting to find natal streams, a remarkable ability that dams and water quality changes can disrupt.
Fish that fail to locate natal spawning habitat due to navigation disruption experience the welfare cost of failed biological drives. Salmon that reach spawning condition and cannot find appropriate spawning habitat face physiological deterioration without reproductive success. The evolutionary drive to spawn is so strong that fish will continue attempting navigation even when conditions make success impossible.