Pacific salmon have a sophisticated way of getting around.
Even young salmon know how to navigate the waters using Earth’s magnetic field to guide them to feeding grounds their ancestors used to frequent. The findings, published in the journal Current Biology, reveal that salmon have an inborn GPS that allows them to find “home.”
"In essence, the fish act as though they have a map based on the magnetic field," Nathan Putman of Oregon State University said in a statement. "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."
Earlier studies have shown that sockeye salmon have a memory of the magnetic field where they first entered the sea after their migration from freshwater rivers and streams. The latest study proved that the salmon rely on both the magnetic intensity and inclination angle of the earth’s magnetic field. By sensing the differences in both characteristics, salmon can position and guide themselves to feeding grounds – even if they are young.
"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.
Pacific salmon perform one of nature’s greatest migrations. After hatching in rivers and streams, they travel thousands of miles to open oceans where they hunt for food before making their way back to their hatching sites, spawn and die.
To prove the salmon’s navigational skills, Putnam and his colleagues built a wooden frame wrapped with copper wires running horizontally and vertically and armed with electrical current to simulate Earth’s magnetic field. Young salmon were placed in large buckets within the frame. Photos taken of the salmon revealed that the fish changed direction in response to changes in the magnetic field.
"Without this ability fish would be forced to wander at random, which could be very costly - wasting energy, or worse, going to unfavorable places that lead to starvation, high predation risk, inappropriate temperatures, etc.,'' Putman told the Vancouver Sun. "Really, the ability for salmon to navigate is what holds their whole life cycle together and makes it possible.''
Salmon aren’t the only species believed to have this inborn navigational sense. The team says other sea creatures such as turtles, sharks and whales may have similar ways of orienting themselves in the ocean.