The sighting of an adult eel in the Sargasso Sea solved a century-old mystery about the creature's migration and reproduction.

Scientists outfitted 28 eels with satellite trackers, and found one reached the Sargasso Sea after a journey of nearly 15,000 miles, Laval University reported. The findings settle a long-lived debate about the location of the only American eel reproduction site.

"Eel larvae have been observed in the Sargasso Sea since 1904, suggesting that the species reproduced in this area, but no adult eels had ever been observed in this part of the Atlantic Ocean," said Professor Dodson of the Faculty of Science and Engineering at Université Laval.

The development of sophisticated satellite transmitters allowed the researchers to observe the eels' migratory path in details never before possible. These transmitters were attached to 22 eels captured in Nova Scotia and 16 from the St. Lawrence Estuary. The data revealed that all of the eels conformed to a similar migratory pattern. When near the coastline, they are believed to have used salinity levels and temperatures to find the high seas.

The eel that reached the Sargasso Sea was observed to turn due south upon reaching the edge of the continental shelf and head straight for the breeding ground.

"This points to the existence of a navigation mechanism probably based on magnetic field detection," Dodson said.

The researchers noted further research is required in order to make a concrete conclusion regarding the eels' migratory route.

"Our data nonetheless shows that the eels don't follow the coastline the whole way, they can cover the route in just weeks, and they do go to the Sargasso Sea. We knew that millions of American eels migrated to reproduce, but no one had yet observed adults in the open ocean or the Sargasso Sea. For a scientist this was a fascinating mystery," Dodson concluded.

The findings were published in a recent edition of the journal Nature Communications.