Story URL: http://news.medill.northwestern.edu/chicago/news.aspx?id=227890
Story Retrieval Date: 4/17/2014 4:34:52 PM CST

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U.S. Fish and Wildlife Service

Adult Chinook Salmon swim in a fish hatchery.


Salmon map migration with the Earth's magnetic field

by Mark Kuykendall
Feb 12, 2014


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U.S. Fish and Wildlife Service.

A salmon swims upstream on the way to its spawning grounds.

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U.S. Fish and Wildlife Service

After swimming upstream to spawn, an adult Chinook salmon ends its life cycle by returning to a shallow stream in Oregon.

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Mark Kuykendall/MEDILL

Salmon fishermen move out of the way as they compete with an approaching grizzly bear for their catch on the Kenai River in Alaska.


Every year, millions of salmon return from traveling thousands of miles across the north Pacific Ocean to the very same rivers and streams in the U.S. and Canada where they were spawned years before. They baffled scientists and fishermen for centuries with their amazing navigational abilities.

But now the secret to one of nature’s greatest migration mysteries has finally been confirmed.

How salmon can navigate from the Aleutian Islands back to Oregon is revealed in a study published this month by researchers at Oregon State University.

“The results are very significant as they resolve a long term uncertainty for the navigation mechanism in Pacific salmon,” said senior scientist David Noakes, a co-author of the study in the February issue of Current Biology. “Our results go beyond the usual correlation studies.”

Known as the “salmon run,” the salmon’s upstream journey to their original birthplace is an annual natural spectacle, drawing thousands of fishermen toward rivers throughout the Pacific Northwest and Alaska. This dramatic end of the salmon’s life cycle has long mystified scientists trying to explain their uncanny sense of direction. Many theorized that salmon must have some sort of special “map sense,” and the Oregon State University research team confirmed just that.

“This opens up a huge suite of opportunities to better understand where these animals go and how they get there,” said researcher Nathan Putman, the lead author of the study. “By gaining information on their ocean migrations we can better predict distributions, forecast returns, and thus better manage this resource.”

The results of the study may have even broader implications, allowing scientists to study and understand the ocean migrations of other species using similar research methods.

“I previously showed this ability with sea turtles,” said Putman. “Given that salmon and turtles are quite evolutionarily distant, this implies that the navigation mechanism arose due to convergent evolution and therefore might be found in other diverse species including tunas, eels, sharks and marine mammals.”

In the study, funded by the Oregon Department of Fish and Wildlife and the Oregon Sea Grant, scientists passed current through copper wires to create a magnetic field in a salmon hatchery. Tiny juvenile salmon were exposed to minor changes in the magnetic field and would change their direction of travel accordingly. The fish responded to these changes by swimming in the magnetic direction that would bring them toward the center of their hereditary feeding grounds.

“Perhaps the biggest implications is that our work shows that ocean navigation in salmon can be studied under laboratory conditions,” said Putman.

Putman was surprised by the advanced level of the natural abilities in the young salmon, originally thinking that this ability might be developed later in life.

“The fish we tested had no prior migratory experience,” he said. “That they come programmed with responses to guide their migration around the North Pacific is quite impressive.”

The results of the study are mostly applicable to Pacific salmon returning from years of maturation in the open seas, but the study may also provide insight into the migration habits of salmon introduced to the Great Lakes region. Chinook salmon from Oregon were introduced into the Great Lakes in the 1960s in order to control the alewife, an invasive species of fish. In turn, they provided a boon to the sport fishing industry.

“Our non-native Great Lakes Chinooks are doing better than anyone initially expected,” said scientist Dan O’Keefe of Michigan Sea Grant. “So the strain of Chinook salmon originally stocked in the Great Lakes must have an inherited magnetic map that is compatible with survival in their new environment.”

For both the Pacific Coast and the Great Lakes, the results of the study are a key piece in the puzzle of understanding salmon behavior, arming scientists and conservation officials with a more comprehensive knowledge to apply toward population management. Salmon are a crucial piece of the economy and the food chain in the Pacific Northwest, and their numbers are closely monitored.