Every European eel is born in one patch of ocean no one has watched

European eels spend most of their lives in rivers and lakes thousands of miles from the sea, then swim all the way to the Sargasso Sea to spawn and die. A Danish biologist traced their larvae back to the region in the early 1900s, but no scientist has ever directly observed wild eels spawning there.

— Johannes Schmidt, The Freshwater Eels — Research findings, 1922-1923