Scientists Track the Epic Migration of Eels for the First Time

October 7, 2016 | Erica Tennenhouse

Photo credit: Ron Offermans/Wikimedia (CC BY-SA 3.0)

European eels use a mix of strategies on their journey to the Sargasso Sea, study finds.

Every autumn, eels depart from European freshwater rivers and embark on a 5,000-kilometer (3,100-mile) journey across the Atlantic Ocean to their spawning ground in the Sargasso Sea. But the precise route they take has been a mystery to scientists, due to a lack of tracking experiments following the eels through their migration.

New data from more than 700 tagged eels over five years shows that they take multiple paths to the Sargasso Sea — some eels follow the shortest line to reach the spawning site in record time, and others meander along less straightforward routes, not reaching their final destination until nearly a year later.

LEARN MORE: World’s Largest Animal Migration Captured in New Documentary

Writing in the journal Science Advances, the authors conclude, “although some eels may be capable of a rapid migration to the Sargasso Sea to spawn in early spring, it seems likely that many eels undertake a slower-paced migration that enables them to arrive in the Sargasso spawning area before spawning begins again the following December.”

As BBC reports, the finding contrasts with the previous assumption that all migrating eels would prefer the shortest, quickest route to their destination.

The migration is the defining activity of the eels’ lives. It is their only chance to reproduce, and once the arduous journey is complete and they release millions of eggs into the Sargasso Sea, they die.

The migration is also fraught with danger for the critically endangered eels — the BBC lists disease, habitat loss, predation, and harm from hydropower turbines as some of the greatest threats they face.

With this new insight into the eel’s migratory strategy, the researchers hope that conservationists will be better equipped to manage stocks to help boost their population in the future. 

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