ShapeShapeauthorShapecrossShapeShapeShapeGrouphamburgerhomeGroupmagnifyShapeShapeShaperssShape

Do Magnetic Signposts Direct Salmon Home?

NORTH CAROLINA, US - How fish find their way back to their birthplace to reproduce after migrating across thousands of miles of open ocean has mystified scientists for more than a century. But marine biologists at the University of North Carolina at Chapel Hill think they might finally have unraveled the secret.

At the beginning of their lives, salmon and sea turtles may read the magnetic field of their home area and "imprint" on it, according to a new theory in the latest issue of the journal Proceedings of the National Academy of Sciences.

The Earth's magnetic field varies predictably across the globe, writes Patric Lanewith, University of North Carolina, every oceanic region having a slightly different magnetic signature. By noting the unique "magnetic address" of their birthplace and remembering it, animals may be able to distinguish this location from all others when they are fully grown and ready to return years later, researchers propose.


*
"Natal homing can be explained in terms of animals learning the unique magnetic signature of their home"
Kenneth Lohmann, Ph.D., professor of biology in the UNC College of Arts and Sciences

Previous studies have shown that young salmon and sea turtles can detect the Earth's magnetic field and use it to sense direction during their first migration away from their birthplace to the far-flung regions where they spend the initial years of their lives.

The new study seeks to explain the more difficult navigational task accomplished by adult animals that return to reproduce in the same area where they themselves began life, a process scientists refer to as natal homing.

"What we are proposing is that natal homing can be explained in terms of animals learning the unique magnetic signature of their home area early in life and then retaining that information," said Kenneth Lohmann, Ph.D., professor of biology in the UNC College of Arts and Sciences and the first author of the study. "We hope that the paper will inspire discussion among scientists and eventually lead to a way of testing the idea."

Lohmann also notes that if the theory is correct, it could lead to new ways of helping save sea turtles and salmon. "Ideally, it might be possible to steer turtles to protected areas where we would like them to nest," Lohmann said, noting the animals' endangered status. "It might also be possible to use magnetic imprinting to help re-establish salmon populations in rivers where the original population has been wiped out."

the Fish Site Editor

Learn more