Salmon use magnetic fields to return home

February 07, 2013

Salmon use magnetic fields to return home

Salmon may rely on magnetic fields to navigate waterways.

A new study has discovered than salmon use the Earth’s magnetic field in order to swim across the ocean to find the stream the fresh water stream they were born in. A group of U.S. Researchers have suggested that the salmon are able to find their birth streams because of a memory of the magnetic field where they first entered the ocean.

Salmon are born in fresh water streams, but soon venture out into the salt water ocean. They then make the grueling trip back to their birth stream in order to begin breeding. Although this process has been extensively studied, no one knew how the salmon’s achieved such a remarkable task.

Now, the new study, which was published in the journal Current Biology, has found that the salmon most likely utilize geomagnetic cues to return to their birth place. In addition to salmon, the scientists believe turtles, seals, and other marine animals may also use similar geomagnetic cue for migrating purposes.

For the study, the research team specifically studied the sockeye salmon, which is native to the northern Pacific Ocean. The migration of the sockeye salmon back to its birth stream is considered one of the most grueling in the entire animal kingdom. As such, scientists have wondered for years how the sockeyes know exactly which stream leading into the ocean they were born in.

The most popular theory was that the salmon use chemical and geomagnetic cues to locate and swim to their place of birth. Despite its popularity, this hypothesis had never been directly studied. That is, until now.

The research team was able to support the geomagnetic hypothesis by studying data collected by fisheries for 56 years. The detailed data recorded information about the salmon that returned from the ocean to their birth place in Fraser River, British Columbia. While studying the fishery logs, the scientists also discovered that the path the fish took around Vancouver Island to get home had the same intensity of geomagnetic field as their birth streams.

For salmon to find their way back home, they remember the magnetic field that exists where they first enter the sea as juveniles, and once they reach maturity, they seek that same coastal location, with the same magnetic field,” Oregon State University researcher Nathan Putman told BBC News. “In other words, salmon remember the magnetic field where they enter the ocean and come back to that same spot once they reach maturity.”

According to Putman, other marine animals in migration may be picking up the same magnetic cues as the salmon. “It seems unlikely that salmon are the only ones who’ve come up with this really good idea for finding your way home – it likely evolved in multiple lineages,” he said.

For now, Putman plans to continue focusing on the salmon. His research team is working on learning more about the geomagnetic cues the salmon follow. They hope that one day their research can help commercial fishing companies.


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