“No human has ever seen eels reproduce; no one has seen an eel fertilize the eggs of another eel; no one has managed to breed European eels in captivity. We think we know that all eels are hatched in the Sargasso Sea, since that’s where the smallest examples of the willow leaf–like larvae have been found, but no one knows for certain why the eel insists on reproducing there and only there. No one knows for certain how it withstands the rigors of its long return journey, or how it navigates. It’s thought all eels die shortly after breeding, since no living eels have ever been found after breeding season, but then again, no mature eel, living or dead, has ever been observed at their supposed breeding ground. Put another way, no human has ever seen an eel in the Sargasso Sea. Nor can anyone fully comprehend the purpose of the eel’s many metamorphoses. No one knows how long eels can live for. In other words, more than two thousand years after Aristotle, the eel remains something of a scientific enigma, and in many ways, it has become a symbol of what is sometimes referred to as the metaphysical.”
―
Patrik Svensson,
The Book of Eels: Our Enduring Fascination with the Most Mysterious Creature in the Natural World — A Natural History