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. 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. The Sargasso is the only place on Earth where they breed. The European eel and the American eel-both considered endangered by the International Union for Conservation of Nature-make this extraordinary migration. 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. 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.

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.

Fishing planet unique european eel