Built-in GPS Aids 4,000-Mile Migration of Pacific Salmon

By: By Michele Berger

Published: February 6,2014

 

 

 

 

 

Juvenile Chinook salmon use the Earth’s magnetic field to orient themselves, a new study from Oregon State University shows. (Tom Quinn and Richard Bell)

Even if juvenile Pacific salmon have never before migrated, they innately know where to go. New research published today in Current Biology reveals that these fish have a sort of built-in GPS system that allows them to position themselves and move according to the Earth’s magnetic fields.
“Before the fish even hit the ocean, they have information about how they should orient to reach, or remain in, favorable locations,” lead researcher Nathan Putman, Ph.D., of Oregon State University, said in a news release. How do they know where to go?
To figure that out, Putnam, along with David Noakes, Ph.D., director of OSU’s Oregon Hatchery Research Center and a team, first looked at more than a half-century’s worth of salmon fishery catches along the Canada-United States border to identify fish swimming routes. By comparing these data to the Earth’s magnetism at key entry points, the scientists learned that where the fish ended up was mostly determined by how closely the magnetic signature resembled that of the previous year.
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With that information in hand, they then created a tank and coil system in the lab that allowed them to manually change the magnetic pull and see in which direction more than 1,000 young fish swam.
“You put the fish in the bucket, let the fish adjust to being there, then switch on the magnetic field,” Noakes told weather.com. “Now you’re suddenly in Alaska. We tell the fish that magnetically they’re north of where they’re supposed to be. They turn around and swim south. If we change the direction and tell them they’re in Hawaii, they turn around and swim north.”
An individual juvenile, he added, has never been anywhere before. Yet “it knows where it is now and it knows where it’s supposed to get to.”
These findings could have implications for where to locate these fish in the ocean. They also suggest that raising Chinook salmon in hatcheries — with iron-reinforced bars in the concrete, for example, or in metal tanks — could mess with the internal compass of the swimmers.
“Juvenile salmon face their highest mortality during the period when the first enter the ocean,” Putman said. “Anything that makes them navigate less efficiently is a concern because if they take a wrong turn and end up in a barren part of the ocean, they are going to starve.”
To view the paper, “An Inherited Magnetic Map Guides Ocean Navigation in Juvenile Pacific Salmon” from Current Biology, click here.
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