Changing Planet

Mystery Solved: Salmon Navigate Using Magnetic Field

Whoever said you can’t go home again has never met a sockeye salmon, which navigates more than 2,485 miles (4,000 kilometers) to spawn in the same stream in which it hatched. (See “5 Amazing Animal Navigators.”)

Now, scientists have finally solved how the species accomplishes its navigational feat—the fish uses Earth’s magnetic field to steer itself home.

Sockeye salmon find their way home by using small changes in the Earth’s magnetic field. Photograph by Tom Quinn, University of Washington


“To find their way back home across thousands of kilometers of ocean, salmon imprint on [i.e. learn and remember] the magnetic field that exists where they first enter the sea as juveniles,” study leader Nathan Putman, of Oregon State University, said in a statement.

“Upon reaching maturity, they seek the coastal location with the same magnetic field.”

Like several other species of salmon, sockeye hatch in many of the streams and tributaries of the U.S. Pacific Northwest.

After hatching, they live and mature in the gravel beds of these freshwater streams for one to three years. Then, the salmon make their way from their freshwater nurseries to the open waters of the Pacific Ocean, where they spend another several years feeding. Eventually the fish make their way back to the streams in which they were born to spawn and begin the cycle anew.

Navigating Salmon a Mystery

What scientists didn’t know was how the salmon managed to do this. Navigating in the open ocean is a difficult task even with a GPS, yet even with such tiny brains, salmon can identify one stream out of several thousand options.

sockeye picture
Sockeye swarm the Adams River in British Columbia, Canada. Photograph by Todd Mintz, Your Shot


So Putman and colleagues hypothesized that salmon were using variations in the Earth’s magnetic field to figure out where “home” was. If this was true, then the researchers could see if a salmon’s ability to navigate changed over time with small, naturally occurring variations in the global magnetic field.

Putman and colleagues used 56 years of fisheries data to study a group of sockeye salmon that spawned in the Fraser River in British Columbia and spent much of their adult lives in and around Alaska‘s Aleutian Islands. The researchers studied the likely routes the salmon took in transit between these two locations and compared it to data on the strength of the Earth’s magnetic field at the time. (Also see Alaska’s Clash Over Salmon and Gold Goes National.”)

The key to this study was a major navigational obstacle the fish had to traverse. Vancouver Island blocks the entrance to the Fraser River, forcing the salmon to swim around either the northern or southern end of the island to get to the spawning grounds (see map below). If the fish really did use the Earth’s magnetic field to navigate, then their choice of routes around Vancouver Island would vary depending on the current strength of the magnetic field at the time.

Map by Nathan Putman, Oregon State University
Map by Nathan Putman, Oregon State University


No Place Like Home

Putman’s hunch was correct: The navigational choice depended largely on which route most closely matched the magnetic signature of the Fraser River when the salmon first left the area for the saltier waters of the Pacific.

“These results are consistent with the idea that juvenile salmon imprint on the magnetic signature of their home river, and then seek that same magnetic signature during their spawning migration,” Putman said in a statement from the National Science Foundation, which helped fund the research.

“As the salmon travel that route, ocean currents and other forces might blow them off course. So they would probably need to check their magnetic position several times during this migration to stay on track. Once they get close to the coastline, they would need to hone in on their target, and so would presumably check in more continuously during this stage of their migration.”

This study, published February 7 in Current Biology, is the first to document an animal’s ability to learn to navigate via the magnetic field. The other animals scientists have studied, like lobsters and birds, either have this knowledge imprinted in them from birth or remember the magnetic signature of home, rather than actually learning to navigate. (Also see “Bats Use Magnetic ‘Compasses’ to Navigate, Study Says.”)

These results help explain why salmon raised in hatcheries so frequently become lost in the ocean. Since many fisheries are crisscrossed with electric wires, magnets, and metallic objects—all of which alter perception of magnetism—the fish never learn the magnetic “feeling” of home.

Putman said the results could also be used to forecast where salmon will be in future seasons by studying how the magnetic field changes over time.

Carrie is a freelance science writer living in Virginia. When she's not writing about cool critters, she's spending time outside, drinking coffee, or knitting. You can visit her website at
  • STaiX

    Really it’s in dangerous moments,That all because of the changments happned by human,:s -.-

  • STaiX

    by the way,today i watched the salmon documantry

  • Henry

    Any maps of salmon ,iteration routes?

  • Henry

    Migration routes

  • kathleen hilman

    Sounds like not just the Earth would be in trouble with big changes in the magnetic poles, but many creatures that depend on the magnetic imprint discussed…

  • Grant Livingston

    This is amazing! What beautiful creatures we must sustain in perpetuity so that we may always eat them 🙂

  • John

    Sharks do this with ampullae of Lorenzini; what do salmon use?

  • Mad Husband

    My wife uses the earths magnetic field in finding me whenever i im not home early.

    My wife is a salmon.

  • Max

    If almon return exclusively to the river of birth then are the salmon from different streams genetically distinct (differentiable)?”

  • void

    yummmy 😀

  • Zombiemaniac007

    Well, looks like my red nucleus has been given a run for it’s purpose ;P…

  • Todd

    I find this article highly American biased as most international salmon experts would know that the Adams River spawning grounds is one of the largest in North America and does deserve study & reference in this article! As quoted on the following link it is also an inspiring and impressive place to view the spawning: “The Adams River has one of the largest Sockeye salmon runs in North America.”

  • carlasabandar

    A salmon may elucidate my compound structure without run it in NMR (nuclear magnetic resonance) ….

  • Jose

    This is “out of this world”, In my opinion, animals SHOULD NEVER BE KILLED just for sport or entertanment. Fishing, hunting, bullfighting, and any other “sport” that involves the killing of defenseless animals SHOULD BE completely BANNED.

  • Chuck

    Either you left out a lot of important details or this reminds me of global warming junk science. Scent is a much more likely methodology.

  • Enigma

    Yeah, those bears have given up on a salmon diet. Irony. But Tom Wolfe was right; you’ve changed and that milieu that was ‘home’ has changed. You can’t go home again, and you’ll never dip your foot in the same river twice.

  • Farrukh

    So, are scientists going to read/interpret the earth’s magnetic filed patterns now, so that we humans can use that to reach back our homes :p

  • RJB

    Ah…become a salmon fisherman, visit interesting places, learn about facinating and exotic creatures…kill and eat them!

  • northamerica

    What is a salmon and what can it do for my oil

  • Mark

    mystery solved in europe in 1957……..

  • Ruth Rosin

    Enough of these stupid clams that various subhuman animals navigate by using the earth magnetic-field! Humans alone can do that, and they can do it only by using a magnetic compass!!!

  • Anti-Ruth Rosin

    Despite the account of humans being what we may call a dominant species with the power of a more advanced communication as well as highly developed technology, there is still a vast amount of information about the universe that is very unknown to us. Although we may use various methodologies to predict a variety of events as well as circumstances, there is no way for us to be one hundred percent certain of anything. Theories are only acknowledged by being backed up with known evidence, there may be forces we are completely unaware of, even though we may assume that we understand any given topic solely based on the fact that we have evidence for it. However, nothing is granted as certain. Magnetic fields have further been proved in the migration of birds, mainly when the skies have clouded over and they have no vision of the sun and cannot follow the direct path. Before supporting or neglecting any theory as a possible truth, it would be suggested that you further educate yourself so that you do not appear as foolish to just believe whatever you may think to be true.

  • Andrea

    To Bad Husband your wife is not a salmon the salmon are river people she is one of the sky people and she is watching you…LOL

  • Joe Cognito

    So what happens when the magnetic poles flip? Every few hundred thousand years or so the earths magnetic fields experience a geomagnetic reversal and the magnetic north and magnetic south poles flip. I wonder how the salmon manage this. Of course, it takes a few thousand years for the flip to occur so maybe its to slow of a process for it to matter to their tiny little fishy brains.

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