European eels migrate to the Sargasso Sea to spawn after spending years in rivers and coastal waters.
The European eel, Anguilla anguilla, has a remarkable catadromous life cycle. Young eels drift across the Atlantic as transparent larvae before entering European and North African waters. They become yellow eels and may live for years in freshwater, brackish water or coastal habitats.
When mature, they transform into silver eels and begin a long migration westward into the Atlantic. Scientists have not observed every stage of spawning directly, but oceanographic evidence and larval distributions identify the Sargasso Sea region as the breeding area. Adults are believed to spawn there and then die.
The young return toward Europe with ocean currents. Barriers, pollution, parasites, fishing and changes in ocean conditions have contributed to major declines, and the European eel is classified as Critically Endangered.