How do eels mate? Once believed to spontaneously spawn, here's how they do it

Once thought to have spontaneously spawned, the mating habits of elusive eels remained a mystery for a long time.

European eels lead double lives that are split between fresh- and salt-water, maturing in rivers and heading to the sea to breed.

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The lack of larvae in rivers led Aristotle to suggest that eels arise spontaneously in river mud, and it was only in 1922 that the Sargasso Sea (a region of the Atlantic Ocean) was eventually identified as the eel’s breeding ground.

How do eels mate?

Male and female eels release sperm and eggs into the water for external fertilisation, and the larvae spend years travelling back across the Atlantic to enter European rivers.

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