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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 picture

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.

Comments

  1. Anti-Ruth Rosin
    A place of intellect.
    March 14, 5:21 pm

    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.

  2. Ruth Rosin
    NYC
    February 8, 1:55 am

    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!!!

  3. Mark
    November 11, 2013, 8:04 am

    mystery solved in europe in 1957……..

  4. northamerica
    NA
    February 21, 2013, 3:46 pm

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

  5. RJB
    NH
    February 21, 2013, 11:17 am

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

  6. Farrukh
    Islamabad
    February 21, 2013, 1:33 am

    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

  7. Enigma
    Wouldn't you like to know...
    February 20, 2013, 1:46 pm

    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.

  8. Chuck
    Arizona
    February 20, 2013, 12:05 pm

    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.

  9. Jose
    GUADALAJARA CITY,(MEXICO)
    February 20, 2013, 10:54 am

    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.

  10. carlasabandar
    Malaysia
    February 20, 2013, 3:22 am

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

  11. Todd
    Calgary
    February 20, 2013, 1:59 am

    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.”
    http://www.env.gov.bc.ca/bcparks/explore/parkpgs/roderick/

  12. Zombiemaniac007
    Malaysia
    February 20, 2013, 12:50 am

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

  13. void
    australia
    February 18, 2013, 5:13 pm

    yummmy :D

  14. Max
    February 17, 2013, 9:37 pm

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

  15. Mad Husband
    February 17, 2013, 1:50 am

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

    My wife is a salmon.

  16. John
    Ohio
    February 14, 2013, 5:01 pm

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

  17. Grant Livingston
    United States
    February 14, 2013, 10:07 am

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

  18. kathleen hilman
    Wyoming, USA
    February 14, 2013, 12:41 am

    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…

  19. Henry
    February 13, 2013, 3:46 pm

    Migration routes

  20. Henry
    alaska
    February 13, 2013, 3:43 pm

    Any maps of salmon ,iteration routes?

  21. STaiX
    February 13, 2013, 2:39 pm

    by the way,today i watched the salmon documantry

  22. STaiX
    Algeria
    February 13, 2013, 2:38 pm

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