Salmon Navigate Home Using Earth's Magnetic Fields

Couple of sockeye salmon just prior to spawning. image courtesy of Vasik Olga / shutterstock. Sockeye salmon put on a lot of miles during their short life. From the freshwater riverbeds where they hatch and spend their first couple years, juvenile salmon travel some 4,000 miles to the ocean where they fatten up for two years before turning around and retracing their steps. But salmon can't leave actual footprints, nor do they have the luxury of dropping waterproof bread crumbs so they can find their way back home. Scientists have long suspected that these big fish instead use the Earth's magnetism to orient their inner compass. A recent study of 56 years' worth of migration data presents pretty convincing evidence for this geomagnetic hypothesis and how it works. The researchers theorized that when the young fish first head out for the ocean they make a mental note of the particular ...