A new discovery shows Pacific salmon inherit a magnetic map from their parents. Even when born in captivity, with no knowledge of the world around them, the fish align themselves in the direction of waterways followed by their ancestors.
In the wild, the young animals would start traveling toward feeding grounds. In captivity, they begin heading in the direction of feeding grounds used by previous generations. This ability to sense magnetic fields is used throughout the life of the animals.
"In essence, the fish act as though they have a map based on the magnetic field. When the fish experience a magnetic field that is north or south of their typical ocean range, they change their swimming direction to go back," Nathan Putman of Oregon State University said.
Salmon are believed to use both the angle and intensity of the Earth's magnetic field in order to determine their location. They then use that information to guide their travel. By being able to tell if they are slightly north or south of their intended locations, for example, the fish can change direction.
"Our findings are certainly suggestive that before the fish even hit the ocean, they have information about how they should orient to reach, or remain in, favorable locations," Putman said. "Everybody was pretty surprised that the fish already had that ability."
The new study of juvenile Chinook salmon (Oncorhynchus tshawytscha) revealed the fish are able to use this natural GPS from the moment they are born. Researchers used electric coils to change the magnetic field in tanks of water, and measured the response of the fish. The salmon were found to be more sensitive to the fields than most biologists believed. By altering the angle or intensity of the induced magnetic field, the biologists were able to identify the method by which the fish pinpointed its position.
Chinook salmon are born in fresh water, but need to head to the open ocean to live out the adult portion of their lives. There, they live several years, before heading back to freshwater in order to spawn in waters near the location they were born. They fish die soon after breeding.
Research on the connection between salmon and magnetic fields was carried out by researchers from Oregon State University, The University of Washington, the University of North Carolina, and the Oregon Hatchery Research Center. These findings may assist the commercial fish industry, that may become more aware of the effect of magnetic materials in salmon hatcheries.
Because Pacific salmon and sea turtles use similar tactics, researchers believe other species may also use the same tools to orient themselves. It is also possible this ability to sense the planet's magnetic field by other animals may be present from the time they are born.