Scientists Establish First Direct Evidence for 100-Year-Old Theory about Enigmatic Eels

How and where European eels migrate to breed is a mystery. Scientists have been puzzled by it since the 4th century BCE! This month, 12 scientists in the UK produced support for a theory proposed nearly 100 years ago. Their report provides the first direct evidence that European eels (Anguilla anguilla) migrate to the Sargasso Sea to breed. 

In the early 1920s, a Danish biologist proposed that the eels breed in the Sargasso Sea. He’d found a concentration of the smallest eel larvae there. But since then, scientists have never found eel eggs or spawning adult eels in the area. So, it was hard to make a complete conclusion. 

That’s what makes the UK team’s report so exciting: it finally confirmed that (at least some) of the adult eels travel to the Sargasso Sea during spawning season.

The scientists captured 26 adult female European eels. Then, they tagged them with pop-up satellite transmitting tags (PSATs). The eels were released back into the ocean. The tag locations showed the eels’ migration toward the Sargasso Sea. Five locations popped up in the sea’s waters. One was directly in the predicted breeding area. 

PSATs have helped scientists better understand the eels’ movements in the past 15 years. The task has become urgent. The European eel is now critically endangered. Its new-population numbers have dropped 95% since the 1980s. 

Now for some fun eel facts! They’re actually a type of fish. They can live for 85 years. And they can slither over land — even climb walls — to get from one water habitat to another.