New research suggests young salmon do not need to learn how to reach the feeding grounds that have been used by their ancestors for generations.
Scientists found the young fish can orient themselves in the direction of their feeding ground using the Earth's magnetic field despite having little to no world experience, a Cell Press news release reported.
"In essence, the fish act as though they have a map based on the magnetic field," Nathan Putman of Oregon State University said in the news release. "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."
In the past migrating sea turtles have been known to use magnetic signals to determine their north-south and east-west positions, before that discovery researchers had doubted migratory animals used magnetic fields to orient themselves. Later researchers determined sockeye salmon also use magnetic fields as a "map."
The team found this map is not based on one specific feature of the magnetic field. It focuses on two aspects: "the magnetic intensity and inclination angle," the news release reported. The fish are believed to have the inherent ability to use subtle changes in both features to navigate.
"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.
The team is unsure exactly how the fish do this, but the fact that they do could be helpful in determining if fish hatcheries should be made from concrete and iron rebar.
"The changes we made in our experiments were not even strong enough to deflect a compass needle," Putman said. "The fields that humans potentially expose fish to are much stronger and could easily overwhelm their ability to perceive Earth's magnetic field at a given location."
