Study: Salmon Use Earth's Magnetic Field To Navigate Home

Feb 8, 2013

Credit EarthFix

During the course of their lives some salmon travel thousands of miles - out to the open ocean to feed and mature. Then, after a few years, they head back to the exact river where they hatched, to spawn the next generation. Scientists don’t fully understand how salmon find their way home, but a new study might provide some more answers.

The answer is magnets - according to a new study in the journal Current Biology.

The earth’s swirling molten iron core creates a magnetic field. It’s constantly shifting, but the field is strongest at the poles. That’s what makes compasses point north.

And sailors aren’t the only ones that use this magnetic force to navigate. Salmon could be using it too.

The study looked at five decades of data on sockeye salmon from the Fraser River in British Columbia.

These fish aren’t any different than other salmon in the northwest – except that on their way home they have to navigate around Vancouver Island, which is about 350 kilometers long.

Nathan Putman is a postdoctoral researcher at Oregon State University and the lead author of the paper. He says the fish can either take the northern route, or the southern route around the island.

“They seem to make that decision based on whichever inlet is more similar to the Fraser River magnetic field in a given year is the one most fish come through,” Putman says.

Putman says salmon remember the strength of the magnetic field at the mouth of their home river.

“What we think the fish are doing is when they’re in a magnetic field that is much stronger than their home magnetic field then that means they need to swim south," he says.

And if the field is weaker they know need to swim north.

That subtle magnetic sense could be enough to tell a Fraser River sockeye to hang a left, or a right when it hits Vancouver Island on the way home.