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Fish navigate using Earth's magnetic fields, study shows


Salmon returning upstream from the sea where they have spent between two and four winters feeding with many covering huge distances to return to the fresh waters to spawn.


Jeff J Mitchell

A new study has suggested fish make their way home using memories of magnetic fields.

Researchers at Oregon State University found that salmon are guided by an internal magnetic map that help them navigate open waters.

“Lots of folks have been wondering for decades how salmon and other animals, like sea turtles or seals and whales, go out in the ocean for a couple of years and then return with remarkable accuracy back to their home,” said study co-author Nathan Putman, reported Wired.

“The magnetic field is an important part of the [salmon's] migratory decision.”

The breathtakingly complex study looked at wild sockeye salmon exiting the Fraser River near Vancouver Island in the Strait of Georgia.

The salmon can choose either to swim up or swim south at that point.

Science Codex said that if salmon did follow the Earth's magnetic fields, their route would vary.

Researchers looked at over 56 years of fishery data to see which way the salmon went each year.

They then compared them to measurements of Earth's geomagnetic fields over the years.

Putman found that the salmon did indeed choose the path with the magnetic field that was most similar to the one they had left two years before, said Wired.

"To find their way back home across thousands of kilometers of ocean, salmon imprint on the magnetic field that exists where they first enter the sea as juveniles," said Putman, reported Science Codex.

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

The findings were published in the journal Current Biology.