Ancient mystery of European eel migration unraveled to help tackle decline of critically endangered species

  • The Environment Agency’s first global research will help tackle the dramatic decline of the critically endangered European eel
  • Adult European eels have been tracked for the first time in the Sargasso Sea, revealing a mystery that has puzzled scientists for centuries
  • Journey of the European eel to its spawning grounds considered one of the most impressive feats of animal migration seen in the wild

A team of researchers led by the Environment Agency has taken a big step towards solving one of nature’s most enduring mysteries: where do European eels breed and how do they get there? -they ?

Having suffered a 95% drop in the number of returns to European rivers since the 1980s, the European eel is now a critically endangered species.

But groundbreaking research published this week gives us a better understanding of the life cycle of this globally important but little-known species and ensures that effective protective measures are in place to combat its decline.

Environment Agency project manager and researcher Ros Wright said:

The European eel is critically endangered, so it is important that we solve the mystery surrounding its full life cycle to support efforts to protect the spawning grounds of this important species.

This is the first time we have been able to track eels to the Sargasso Sea and we are delighted to have the first direct evidence of adult European eels reaching their spawning grounds. Their journey will reveal information about eel migration that has never been known before.

The journey of European eels to their breeding ground in the Sargasso Sea can reach 10,000 km and is considered one of the most impressive feats of animal migration observed in the wild. It’s a mystery that has perplexed scientists for centuries, with the earliest recorded evidence of scientists examining this phenomenon dating back to the 4th century BC.

Working with the Zoological Society of London, Defra, Cefas, Natural England, University of the Azores and Denmark’s University of Technology, the Environment Agency has produced the first-ever direct evidence of European eels roaming the 2,500 last kilometers of their journey. So far, no eggs or eels have been found to confirm this spawning ground.

In December 2018 and 2019, researchers fitted 26 female large European eels with satellite tags and released them from the Azores into the Atlantic Ocean. The Azores islands are near the farthest known point on the eel migration route that has been followed by previous projects.

Programmed to detach and transmit their data after 6 to 12 months, data was received from 23 satellite beacons at different stages of the journey, with six tagged eels reaching the Sargasso Sea. Data transmitted from these beacons reveal that eels have been steadily migrating to the Sargasso Sea and, remarkably, this journey to their breeding grounds takes over a year.

After the eels have spawned in the Sargasso Sea, their larvae return to the UK and other European waters via a different route, carried by ocean currents on the North Atlantic Drift. They then migrate into the rivers as glass eels.

Unraveling the navigational mechanisms, routes taken and locating the spawning grounds of eels is key to understanding the reasons for their decline and putting in place targeted conservation measures to protect this globally important species.

The chair of the IUCN Eel Specialist Group, Matthew Gollock of the Zoological Society of London, said:

European eel populations are at an all-time low and the more we understand about their life history, the better able we are to develop conservation measures to address the critical state of the species.

Professor José Manuel N. Azevedo from the University of the Azores said:

This discovery highlights the role of the Azores in the life cycle of eels. This will help scientists and conservationists push for action to restore eel habitats across the archipelago.

The Environment Agency and its partners will now carry out further analysis of satellite beacon data to uncover further clues about how the eels make their way to their spawning grounds. This is part of an ongoing project and field teams have returned to the Azores to satellite tag eels with extended life tags to reveal more data on silver eel migration and spawning sites. spawning in the Sargasso Sea.

The Environment Agency continues to conduct research into all life stages of the European eel to inform conservation action. This complements work around England to protect eels, for example improving the design of eel passes to improve eel passage upstream in our rivers.

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