The Book of Eels: Our Enduring Fascination With the Most Mysterious Creature in the Natural World

Patrik Svensson weaves together two narratives: the centuries-long scientific quest to understand the European eel (Anguilla anguilla) and his own memories of fishing for eels with his father along a stream in southern Sweden. The book explores what the eel's resistance to human knowledge reveals about curiosity, faith, and the bonds between fathers and sons.

Svensson opens by describing the eel's extraordinary life cycle. Eels are born in the Sargasso Sea, a vast region of the northwest Atlantic bounded not by land but by four ocean currents. They hatch as tiny, transparent larvae called leptocephali and drift on the Gulf Stream for up to three years before reaching Europe, where they transform into glass eels and travel up rivers. In freshwater, they become yellow eels, living solitary, nocturnal lives for 15 to 30 years or more. When some unknown signal triggers reproduction, they undergo a final metamorphosis into silver eels: Their eyes enlarge, their digestive systems shut down, and their reproductive organs develop for the first time. They swim back across the Atlantic, spawn, and die. No human has ever witnessed eels mating or observed a mature eel at the spawning grounds, a gap in knowledge scientists call "the eel question."

Alongside the eel's biology, Svensson introduces his childhood. He and his father drove to the stream at dusk in August, set homemade fishing lines called spillers, and returned at dawn to check them. They rarely spoke. His father told stories about the Sargasso Sea as though it were a fairy-tale world, and every time they caught an eel, Svensson looked into its eyes, trying to see what it had seen.

Svensson traces the eel question back to Aristotle, who in the fourth century BCE concluded that eels spring spontaneously from mud. Despite his pioneering zoological work Historia Animalium, Aristotle found no reproductive organs and declared eels sexless. His error persisted for centuries until the Italian physician Francesco Redi challenged the concept of spontaneous generation in the 17th century. A breakthrough came in 1777, when Carlo Mondini, an anatomy professor at the University of Bologna, provided the first accurate description of a female eel's reproductive organs. The male organs, however, remained elusive.

Svensson recounts how 19-year-old Sigmund Freud, dispatched in 1876 to a marine research station in Trieste by his zoology professor Carl Claus, spent nearly a month dissecting over 400 eels in search of male reproductive organs and found nothing. Svensson notes the irony that the eel concealed its sexuality from the man who would later define modern thinking about sex, and suggests Freud's failure may have contributed to his eventual turn from natural science to psychoanalysis. A sexually mature male eel was not found until 20 years later, off Sicily.

The memoir chapters reveal a father who worked as a road paver his entire life, muscular and tar-stained, who identified as a "worker" by inheritance rather than choice. He had grown up on a tenant farm, dropped out of school, and spent his days spreading asphalt. Svensson hints that the man his father called "Father" was not his biological father, and that the eel-fishing ritual may have been the father's own creation, a way of forging the bond he had never experienced. The father loved animals, believed humans had both power over and responsibility for other forms of life, and killed efficiently but with respect.

Svensson devotes a central chapter to Johannes Schmidt, a Danish marine biologist who in 1904 set off to find the eel's birthplace by tracing ever-smaller larvae across the Atlantic. Schmidt, who lost his father at age seven and grew up connected to the Carlsberg brewery's research laboratory through his uncle Johan Kjeldahl, spent nearly two decades on the search. He enlisted commercial freighters to drag nets, lost his schooner Margrethe in the Caribbean in 1914, and waited out the First World War. By catching progressively smaller larvae as he moved west, Schmidt pinpointed the Sargasso Sea as the breeding ground. His findings, published in 1923, remain the foundation of eel science.

Svensson surveys eel-fishing cultures across Europe, from the ancient system of fishing rights along Sweden's eel coast to the Basque fishermen catching glass eels from Spain's River Oria and the Catholic fishermen of Lough Neagh in Northern Ireland, who formed a cooperative in 1965 to reclaim rights confiscated by British colonizers centuries earlier. These communities face a shared paradox: They argue that banning eel fishing will destroy irreplaceable traditions and that without human engagement with the eel, the species itself will be lost.

The eel's unsettling cultural presence receives extended treatment. Svensson recounts how the Patuxet man Tisquantum saved the starving Mayflower pilgrims by gifting them eels, yet the eel was erased from American mythology. He traces the eel through Günter Grass's The Tin Drum (1959) and Graham Swift's Waterland (1983), connecting the creature to Freud's concept of "the uncanny," the unease felt when something familiar becomes unfamiliar. Svensson also discusses Rachel Carson, the pioneering marine biologist whose first book, Under the Sea-Wind (1941), anthropomorphized an eel named Anguilla to convey the creature's experience, and whose final book, Silent Spring (1962), exposed the devastation of pesticides and helped launch the environmental movement.

Svensson reflects on the eel's apparent ability to cheat death, recounting incidents in which eels found cold and seemingly lifeless revived upon being returned to water. He connects these moments to the concept of faith, suggesting that the eel, like religious belief, offers a promise that transformation and continuity exist beyond what reason can explain.

The eel's decline has been steep. Glass eel arrivals in Europe are now roughly five percent of late-1970s levels, and the International Union for Conservation of Nature (IUCN) classifies the European eel as critically endangered. Threats include the herpes virus anguillae, spread through imports; the parasitic nematode Anguillicoloides crassus, which damages the swimming bladder; industrial pollutants like polychlorinated biphenyls (PCB); hydroelectric dams whose turbines kill up to 70 percent of passing eels; overfishing; and climate change. Svensson places the eel's plight within a potential sixth mass extinction, drawing on journalist Elizabeth Kolbert's The Sixth Extinction (2014). He draws parallels to species already lost: the dodo, exterminated within a century of its discovery on Mauritius, and Steller's sea cow, a giant marine mammal hunted to extinction just 27 years after its discovery in 1741.

In the final chapter, Svensson narrates growing apart from his father as he leaves for university. His parents buy a cabin by a small lake, where they fish but never catch a single eel. The father falls ill with cancer at 56, caused by years of working with asphalt. During his illness, Svensson's mother reveals a long-held secret: The man Svensson called Grandad was not his father's biological father. His father's biological father was someone none of them knew. The father had chosen his own origin story, accepting as his father the man who had been there, on the farm by the stream, and never discussed the truth, even while dying.

The cancer returns twice more. During the final relapse, Svensson notices his father's eyes turning yellow, a sign of liver failure. On July 3, he sits at his father's bedside in hospice, holding his hand, listening to breathing that grows fainter until it stops. After the funeral, Svensson goes to the family cabin and leaves a fishing rod by the lake. When he returns, something is pulling toward the water. He grabs the rod and feels the familiar undulating resistance. As the line catches in rocks by the shore and he peers into the murky water, an eel slithers up from the shadows, looks at him, frees itself from the hook, and disappears into the depths. What lies hidden beneath the surface is a secret, and now it is his.