Today, I learned that eels are fish. This was a disappointment. I knew of fish, I knew of snakes, yet I always assumed eels were some secret third thing. But, nope, they’re just fish. Or are they? A little digging revealed that eels are deeply weird fish, and to my great satisfaction, the secrets I sensed in them run stranger and deeper than their “fish” label suggests.
Let’s dive right in: we don’t really know where eels come from. Which is strange, because they’re everywhere—rivers, lakes, oceans. We only have the faintest sense of where they spawn or how. Their lives remain partly hidden, and that blank space has always invited stories.
Aristotle thought they slithered out of mud, giving the primordial ooze its first big break. Another tale claimed they rose from sea foam, like a grotesque remix of Aphrodite’s birth. Japanese folklore said eels began as earthworms blessed by the summer moon—plausible enough, if you consider being transformed into something both hideous and delicious a blessing. For millennia, our relationship with eels was governed by fables and speculation. Eventually, real science needed to step in.
One spat of scientific interest in eels came at the end of the 19th century. Scientists, lit up by the potential of Darwin’s new theory of evolution, believed they finally had the tools to crack the case: where eels mated, where they were born, where they went to die. They observed. They dissected. And time after time, they kept hitting dead ends.
Here’s the story of one such wall. The year is 1876, in the port of Trieste, Italy—then part of the Austro-Hungarian Empire. In a small lab, surrounded by jars of eels, briny seawater, and plenty of slime, a young zoology student works under orders from his doctoral advisor. His task: to solve the mystery of eels by capturing live specimens from the harbor and dissecting them in search of testes. (The sexual mysteries of eels were anatomical as much as behavioral.) Day after day, he probed and sliced, logging hours at the dissection table. Four months later, he left empty-handed, without so much as a glimpse of a gonad. Upon his departure he wrote: “All I see when I close my eyes is the shimmering dead tissue, which haunts my dreams…”
That student was Sigmund Freud, who later established psychotherapy as a discipline, using dream interpretation to uncover the hidden sexuality of his patients—truths beneath the surface that, like eel gonads, couldn’t be found through straightforward empirical methods. To overstate it: Freud went a little screwy looking for eel balls. (Or maybe he was already screwy enough to go looking for them.) The psychological case study almost writes itself: the same hidden drives that pushed a young researcher to spend four months searching for eel testes might also fuel a lifetime of theories about libido, repression, and desire. The link is tenuous, of course, but it’s fun to imagine the past 150 years of psychotherapy springing from Freud’s failed eel dissection project.
All these years later, no one has ever seen an Anguilla eel do the nasty. But scientists think they’ve at least found the place where it happens: a single location on earth where, strangely enough, no adult eel has ever been spotted. Deep in the Atlantic lies the Sargasso Sea—the only sea without land boundaries, defined instead by four great currents. Eels are born, quite literally, in the Bermuda Triangle.
The mystery cracked a little in 1896, about 20 years after Freud’s attempts, when Italian zoologist Giovanni Battista Grassi found a mature male eel with testes and sperm. He also linked a strange, transparent fish called the Leptocephalus to the eel, noticing they shared the same oddly high number of vertebrae. Long thought to be its own species, the Leptocephalus turned out to be the eel’s larval stage—a dramatic transformation we’d never witnessed since it happens far below, in the deep ocean.
Here’s what we now know: Eels begin as tiny, glassy specs suspended in the Sargasso’s deep blue. They drift for years, feeding on “marine snow” as currents carry them westward. By the time they reach Europe, they’ve transformed into glass eels—longer, flatter, translucent, with a defined backbone.
Then comes the climb out of the ocean. Glass eels push upstream into estuaries, crawling over rocks and mud to find fresh water for their next metamorphosis. There, they shift again into elvers. The translucent jelly of their body becomes speckled with pigmentation, and they develop an insatiable appetite. After a couple of years they bulk up into yellow eels. This adolescent form is the familiar eel seen wriggling in ponds, drawn up from wells, or fished from rivers. Eels can linger in their yellow form for decades, but eventually nature calls them to the ocean again.
Upon their last metamorphosis, eels begin “silvering”: shedding their color for black and chrome. It is now time to head to the ocean to breed. Their eyes get larger to be able to see better in the depths. Their stomach dissolves—won’t be using that. And finally (poor Freud), the eels’ sex organs develop. The eels swim thousands of miles back to the Sargasso, where they release billions of eggs and sperm into the Bermuda Triangle and die. Their young hatch as tiny glass specs adrift in the currents, and the cycle begins again.
So the next time you order unagi and salmon rolls, think about how the paths of their lives mirror one