Dr. Tom Quinn, University of Washington
When sockeye salmon migrate from salt water to fresh water, they change color--going from their ocean colors of mostly silver with some darker coloration on their backs (like a lot of other ocean fish) to red when in fresh water.

Mother Earth’s Magnetism Guides Spawning Sockeye Salmon Home Like GPS: Study


Salmon are known for their homing skills, returning annually to the streams they hatched in to spawn.

What has been something of a mystery, at least until recently, is how they did so. Their journey of thousands of miles across open ocean is undertaken years after they’ve left their rivers of origin.

Scientists at Oregon State University (OSU) studied 56 years worth of fisheries data on the sockeye salmon to British Columbia’s Fraser River. They found that the fish chose routes around Vancouver Island that varied based on fluctuations in the geomagnetic field.

In other words, Mother Earth is their GPS.

“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,” said the study’s lead author, Nathan Putman, a post-doctoral researcher at Oregon State University, in a statement. “Upon reaching maturity, they seek the coastal location with the same magnetic field.”

Basically, the scientists said, the Earth’s “predictable, consistent geomagnetic field” gets almost imperceptibly weaker the closer one gets to the Equator, subject to geomagnetic field drift, as Smithsonian Magazine said. What set the Fraser River apart in terms of approach was the fact that there are two approaches, both around Vancouver Island, which blocks the river’s entrance. The fish would have had to pick one or the other, and they consistently chose the route that most closely matched the magnetic strength and signature of the Fraser River at the time they left, the researchers said.

The theory is that salmon imprint the magnetic field as a waypoint when they leave their home river system, Putman said. It gets them into the general vicinity of the same river system when they return, “and then other, finer cues may take over.”

Their results were published in the journal Current Biology on February 7.

You need to be logged in in order to post comments
Please use the log in option at the bottom of this page



Joetta's picture
Submitted by Joetta on
Wow! What a discovery! Congrats to all the hard work of the scientists and assistants who worked on this project. Now we know how other animals find their way back, also. Right?

Donna McCarty's picture
Donna McCarty
Submitted by Donna McCarty on
Hasn't it also been learned that the salmon imprint on the chemical make up of the water where they hatched and that it is distinct providing a trail for them to follow. That is why hatched salmon released in a different location still return to the water where they hatched more often than where they were released. Anyway, that's what I read and understood also from Oregon studies.