European eel, Anguilla anguilla. (Photo: David Curnick)

An 'internal GPS' would guide eels in their migration to European rivers

UNITED STATES
Friday, April 21, 2017, 02:30 (GMT + 9)

National Oceanic and Atmospheric Administration (NOAA) scientists have discovered that European eels have a sort of internal GPS or global positioning system tuned to the Earth’s magnetic field, which they use as a map to orient themselves during their long ocean journeys.

Born in the Sargasso Sea, that Atlantic Ocean gyre east of Bermuda, this specimen will travel 4,000 miles to the freshwater rivers of Europe.

The researchers of this new study on European eels theorize the American eel might also tune into the magnetic field to assist its migration.

Almost indistinguishable from the European eel, the American eel is also born in the Sargasso Sea. It makes a similar long-distance migration to North American freshwater rivers.

The findings may help improve management of this commercially and culturally important species of eel, as well as similar species, such as the American and Japanese eel. All these eel populations are considered depleted due to fishing pressure, loss of habitat because of dams that block their passage, pollution and changes in ocean conditions.

An international team of scientists who joined Nathan Putman, a post-doctoral researcher at Oregon State University, in his research work, tested the European eels’ mapping skills by exposing juveniles in a laboratory to a series of magnetic fields that mirrored the various magnetic conditions found along the eels’ migration route.

In this way, the scientists found that eels’ orientation differed depending upon the magnetic conditions, but in each case, the eels headed into what would have been the Gulf Stream – a powerful current that is thought to propel young eels from the Sargasso Sea toward Europe.

European, Japanese, and American eels have been fished for centuries to support valuable commercial, recreational and subsistence fisheries.

Juvenile eels just entering freshwater can fetch staggering prices – in some years more than USD 2,000 per pound for eels caught in Maine.

In 2014, total US commercial eel landings were valued at approximately USD 9.8 million.

Putman’s earlier research showed many marine animals, such as Pacific salmon and sea turtles, use Earth’s magnetic field as a large-scale map. By learning what environmental cues animals use to guide their movements, scientists can better predict changes in their migratory routes and distribution.

More research is likely to also contribute to better management of other valuable fisheries for migratory species such as tunas, sailfish, swordfish and sharks.
 
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