After a hundred years of debate, a team of Canadian scientists has proved that American eels (Anguilla rostrata) really do migrate to the Sargasso Sea to reproduce.
The American eel (Anguilla rostrata). Image credit: U.S. Fish & Wildlife Service.
“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 Prof. Julian Dodson of Université Laval, Canada.
Several expeditions aimed at catching adult eels in their gathering site have all failed, but the recent development of sophisticated satellite transmitters opened up new opportunities for scientists.
Prof. Dodson and his colleagues from Dalhousie University, the Institut Maurice-Lamontagne and Université Laval, affixed these transmitters to 22 eels captured in Nova Scotia and 16 from the St. Lawrence Estuary.
In the ensuing weeks, 28 of these transmitters resurfaced in different areas of the Atlantic and transmitted the data they had recorded.
Analysis of the data revealed that all the eels adopted similar migratory paths and patterns.
Near the coastline they appear to use the salinity level and temperature to find the high seas.
A single eel provided data for the ocean segment of the migration. Its transmitter showed that it turned due south upon reaching the edge of the continental shelf, and headed straight to the Sargasso Sea.
In 45 days, this individual captured in the province of Quebec covered 1,490 miles (2,400 km).
“Eight eels were successfully tracked to the open ocean off the continental shelf, including one tracked for 1,490 miles to the northern limit of the spawning site in the Sargasso Sea,” the scientists said.
“This points to the existence of a navigation mechanism probably based on magnetic field detection,” added Prof. Dodson, who is the senior author of a paper in the journal Nature Communications.
“Our results represent the first direct evidence of adult Anguilla migrating 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,” Prof. Dodson said. “For a scientist this was a fascinating mystery.”
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Mélanie Béguer-Pon et al. 2015. Direct observations of American eels migrating across the continental shelf to the Sargasso Sea. Nature Communications 6, article number: 8705; doi: 10.1038/ncomms9705
