Every year, the European eel embarks on a remarkable migration journey, with its final destination being the Sargasso Sea in the North Atlantic, where it spawns once before dying.
For a long time, scientists have speculated that the Sargasso Sea off the coast of North America is the ultimate destination in the 6,500 km migration of the glass eel (Anguilla anguilla), also known as the European eel. However, no concrete evidence has proven this until now.
The population of European eels has declined by over 90% across the continent in the past 30 years. (Photo: Reuters).
Critically Endangered
Thanks to modern technological devices, this hypothesis has finally been confirmed. By attaching satellite tracking devices to European eels, scientists have been able to monitor this species during the final leg of their annual migration.
This information will aid in the conservation of the European eel, a species that is currently on the brink of extinction.
“This is the first time we have been able to track European eels in the Sargasso Sea, and we are thrilled to have the first direct evidence of adult European eel activity in their spawning area,” said Ros Wright from the Environment Agency in the UK, who leads the research.
“This journey will reveal information about the migration of European eels that has never been known before,” Mr. Wright added.
Despite having a lifespan of several decades, European eels are currently facing numerous threats. Changes in ocean currents due to climate change, pollution, and overfishing have led to a significant decline in their population across the continent.
Additionally, the construction of dams and hydropower projects has obstructed their migration to the sea for spawning.
Dan Hayter, an expert on European eels at the Environment Agency in the UK, has been monitoring this species in the Blackwater River in Essex. He has witnessed their alarming decline over the past 20 years.
“We catch European eels here every year. Compared to historical numbers, the current yield is very low and has decreased by 95% since the 1980s,” Mr. Hayter stated.
Scientists check the habitat indicators of European eels on the Thames River, London. (Photo: European Eel Foundation).
Although they are endangered, European eels, especially the juveniles, are still considered a delicacy in Spain and some East Asian countries. The trade of juvenile eels is illegal, making smuggling this commodity highly profitable.
At the end of September, Europol arrested 29 individuals in Spain and 20 others across Europe after seizing 180 kg of juvenile European eels. The black market value of this shipment was approximately 237,000 euros.
According to authorities, the smuggling of European eels has significantly increased since the lifting of restrictions on frozen goods imports (due to Covid-19).
Important Discovery for Conservation Efforts
“Criminal organizations have returned to the illegal export of European eels, camouflaged in carry-on luggage or, in special cases, hidden in oxygen-filled bags. We are also monitoring shell companies set up solely to transport eels hidden in frozen foods. We want to remind everyone that the export of eels is strictly prohibited,” the Spanish police stated in a press release regarding the incident.
In 2020, Gilbert Khoo, a British seafood trader, was charged after police discovered he illegally exported juvenile European eels worth £53 million from London to Hong Kong.
About three years after being born in the Sargasso Sea, juvenile European eels will return to the coasts of Europe while still very small. At this stage of their life cycle, their bodies are transparent—hence they are called “glass eels.”
They will begin to adapt to freshwater and mature in rivers. They grow to about one meter in length and will remain in the rivers until they are ready to swim back to the sea to spawn and then die.
Due to the extensive area covered by the spawning migration of European eels in the Atlantic, it is challenging for scientists to capture what happens during this phase. Previous studies could only track adult eels as they arrived in the Azores archipelago of Portugal.
However, scientists have now been able to attach tracking devices to mature European eels in the Azores, and results show that they can swim all the way to the Sargasso Sea across the Atlantic.
“Previously, we knew that European eels could swim to the Azores, but what happens afterward has remained unexplored,” Mr. Wright said.
After drifting in the ocean for 3 years, juvenile European eels will return to the rivers of Europe. At this stage, they are referred to as “glass eels” and are a highly sought-after delicacy. (Photo: European Eel Foundation).
“We believe that if we can attach tracking devices in the Azores, we will resolve that mystery. And we have done it—tracking the final leg of the journey to the Sargasso Sea,” Mr. Wright added.
Identifying the spawning area of the eels is crucial as it will help scientists uncover the reasons for the species’ decline and implement necessary conservation measures.
