Scientists unlock a secret of Chinook salmon's uncanny GPS

Scientists have confirmed that ocean salmon can navigate by sensing the Earth’s magnetic field, which helps them navigate across thousands of miles of water without getting lost.

Courtesy of Tom Quinn, co-author on the paper, and Richard Bell
A Chinook parr salmon. A paper published in an upcoming issue of Current Biology demonstrates that salmon have the ability to sense magnetic fields.

The next time you use a GPS, keep in mind that there are creatures on this planet that have one built in.

New research finds that ocean salmon can detect Earth’s magnetic field. They use this ability to navigate across thousands of miles of water without getting lost.

It helps them to leave their river of origin, temporarily migrate to oceans to feed and get bigger, and come back to the same river to lay eggs, says Nathan Putman, a postdoctoral researcher in Oregon State University’s Department of Fisheries and Wildlife and lead author on the study.

In a study that will be published this month in the forthcoming issue of Current Biology, scientists confirmed the link between salmon behavior and the Earth’s magnetic field.

During a series of experiments at the Oregon Hatchery Research Center in the Alsea River basin that served as the test site, researchers exposed hundreds of juvenile (about six months old) Chinook salmon to certain magnetic fields and noted the direction in which the salmon swam.

We picked up the magnetic fields that exist at catch areas within the Pacific Ocean, Dr. Putman told the Monitor. In other words, there are areas in the Pacific Ocean where salmon are found in abundance. Beyond that point, salmon are not found, he says. Assuming that this point serves as the northern limit of the oceanic range of Chinook salmon, they are more likely to swim in a southerly direction, while fish encountering a far southern field tended to swim north, he adds.

To create a magnetic field, scientists passed electrical current through copper wires that ran horizontally and vertically around the perimeter of a large wooden platform and the salmon were placed in five-gallon plastic buckets on the platform

After exposing the hundreds of juvenile Chinook salmon to simulated magnetic fields that exist at the latitudinal extremes of their oceanic range, researchers observed that a majority of the “fish presented with a magnetic field characteristic of the northern limits of the oceanic range of Chinook salmon were more likely to swim in a southerly direction, while fish encountering a far southern field tended to swim north,” according to a press release from the Oregon State University. And when the magnetic field of test site was applied, these fish did not seem to have any directional preference, he said.

This indicates that the fish posses a “map sense” which directs their navigation and tells them which way to swim. 

“What is particularly exciting about these experiments is that the fish we tested had never left the hatchery and thus we know that their responses were not learned or based on experience, but rather they were inherited,” Putman said.

The fish responded to the magnetic field which was not strong enough to deflect a compass needle, he said. Moreover, “these fish were only exposed to the magnetic field we created for about eight minutes.”

Weakening of the earth’s magnetic field will influence such creatures that depend on the magnetic field for navigation, he says. But the magnetic field is likely not the only tool salmon use to find their way,  Putman said.

“They likely have a whole suite of navigational aids that help them get where they are going, perhaps including orientation to the sun, sense of smell and others,” he said.

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