The Geomagnetic Map of Juvenile Salmon

Numerous marine animals undergo ontogenetic shifts in habitat utilization, maximizing fitness by exploiting distant oceanic regions that are more favorable during a particular life-stage. The navigation mechanisms that underpin such life-history strategies, however, are poorly known. Accumulating evidence indicates that diverse animals use positional information from the Earth’s magnetic field for navigation. Laboratory-based experiments demonstrate that juvenile Chinook salmon, steelhead trout, and Atlantic salmon perceive magnetic cues that could be used as a proxy for geographic position. “Simulated magnetic displacements” indicate that salmon use both the inclination angle and intensity of the magnetic field to derive positional information – even when other sensory information (e.g., visual, olfactory, auditory, and inertial) remains characteristic of the home location. Simulations of the observed orientation responses within a high-resolution ocean circulation model are consistent with the hypothesis that these fish use the magnetic field to locate favorable oceanic habitat. The results in salmon, paired with similar findings in sea turtles, imply that magnetic maps are phylogenetically widespread. Exploring similar navigational mechanisms in other long-distance migrants may reveal commonalities in movement patterns for diverse marine species.