Scientists have long theorized that salmon use magnetism to find their way home, but there’s never been any evidence to prove this theory true – until now. According to scientists from Oregon State University in Corvallis, their recent study confirms that salmon really are using the Earth’s magnetic field to navigate their way home to spawn each year.
After hatching in freshwater streams, young salmon head for the ocean, but before leaving their home stream, the fish imprint their native river’s magnetic field. They then head out into the deep blue ocean and live for years, covering thousands of miles before it’s time for them to head back to the very same stream they were born. Using the Earth’s magnetic field to help them find their way back, they then lay eggs of their very own in their native stream.
Nathan Putman, a postdoctoral researcher at Oregon State University of Corvallis, magnetic detection “is one part of their toolkit for being really effective navigators.” He shared this information in Thursday’s edition of Current Biology.
But magnetism isn’t the only way that salmon navigate the streams, researchers say. They believe that salmon also use their sense of smell to help them locate the exact stream they were born in.
This new knowledge may help scientists understand why salmon stocks have been on the decline, and why certain odd events, like the failure of millions of wild sockeye failed to return to Canada’s Fraser River in 2009. Putman suggested that it’s possible that events such as this occurred because of a possible glitch in the salmons’ navigational abilities.
Researchers feel this new information will also help them address an even bigger concern – whether or not salmon being raised in hatcheries have an altered “internal GPS.” Hatchery salmon, which account for a large amount of the “wild salmon” population that ends up on the dinner plate of humans, are hatched in tanks. They are then released into streams and rivers.
Putman worries that these hatchery-raised salmon have their magnetic imprinting thrown off by man-made products, like the iron reinforcements used in the fish tanks or nearby electrical cables. He says this would explain continued decline of the real wild salmon population.
“They might not be very good at navigating, and that could cause problems ,” he said.
What’s more, if the fish born in hatcheries get lost on their way home, they may end up interbreeding with real wild salmon populations. Because studies suggest that hatchery-raised aren’t as good at surviving outside of captivity, mating between hatchery fish and wild fish could genetically weaken the wild salmon population over time.