"To save endangered eels, researchers have been working for decades to figure out where they reproduce."
"Every three years, Reinhold Hanel boards a research ship and voyages to the only sea in the world that’s located in the middle of an ocean. The Sargasso, bounded by currents instead of land, is an egg-shaped expanse that takes up about two-thirds of the North Atlantic, looping around Bermuda and stretching east more than 1,000 kilometers. Dubbed the “golden floating rainforest” thanks to the thick tangles of ocher-colored seaweed that blanket the water’s surface, the Sargasso is a slowly swirling sanctuary for over 270 marine species. And each year, the eels arrive.
The European eel and the American eel—both considered endangered by the International Union for Conservation of Nature—make this extraordinary migration. The Sargasso is the only place on Earth where they breed. The slithery creatures, some as long as 1.5 meters, arrive from Europe, North America, including parts of the Caribbean, and North Africa, including the Mediterranean Sea. Hanel, a fish biologist and director of the Thünen Institute of Fisheries Ecology in Bremerhaven, Germany, makes his own month-long migration here alongside a rotating cast of researchers, some of whom hope to solve mysteries that have long flummoxed marine biologists, anatomists, philosophers, and conservationists: What happens when these eels spawn in the wild? And what can be done to help the species recover from the impacts of habitat loss, pollution, overfishing, and hydropower? Scientists say that the answers could improve conservation. But, thus far, eels have kept most of their secrets to themselves.
The idea that eels have sex at all is a fairly modern notion. Ancient Egyptians associated eels with the sun god Atum and believed they sprang to life when the sun warmed the Nile. In the fourth century BCE, Aristotle proclaimed that eels spontaneously generated within “the entrails of the earth” and that they didn’t have genitals."