The Book of Eels

The Book of Eels Plot Summary

Introduction

In the cool, shadowy depths of European rivers and lakes, there exists a creature so enigmatic that it has perplexed scientists for millennia. The European eel, with its serpentine body and inscrutable eyes, has been the subject of scientific inquiry since the time of Aristotle, yet many aspects of its life remain shrouded in mystery. Unlike most animals whose life cycles are well-documented, the eel seems to deliberately obscure its most intimate secrets from human observation. No scientist has ever witnessed eels mating in their natural habitat, and until relatively recently, no one knew where they were born or how they transformed through their remarkable life stages. The story of the European eel is not merely a tale of biological curiosity—it represents one of the most extraordinary migrations in the animal kingdom. From the mysterious Sargasso Sea in the western Atlantic to the freshwater streams of Europe, eels undertake a journey spanning thousands of miles and multiple metamorphoses. This book takes you on this remarkable odyssey, exploring how humans have attempted to understand this creature throughout history, from ancient superstitions about eels spontaneously generating from mud to modern scientific expeditions. Along the way, we'll discover how the eel has influenced not just natural science but also human psychology, literature, and culture, becoming a powerful metaphor for the mysteries that persist even in our age of scientific enlightenment.

Chapter 1: The Enigma of Eel Reproduction: A Centuries-Old Mystery

The question of how eels reproduce has confounded some of humanity's greatest minds for over two thousand years. Aristotle, often considered the father of zoology, was utterly baffled by eels. After careful observation and dissection, he concluded that eels must spontaneously generate from mud, as he could find no reproductive organs or eggs within their bodies. This theory, remarkable as it sounds to modern ears, remained the dominant explanation for centuries. Throughout the Middle Ages and into the Renaissance, theories about eel reproduction ranged from the creative to the absurd. Some believed eels were born from dew drops that fell on certain plants near water. Others thought they emerged from the hairs of horses' tails that happened to fall into ponds. In parts of Europe, it was commonly believed that eels were the offspring of water snakes or formed from the decomposing bodies of other eels. The mystery persisted because no one had ever observed eels mating or found eel eggs or young in freshwater habitats. The first scientific breakthrough came in the late 18th century when Italian researcher Carlo Mondini finally discovered ovaries in female eels. Yet this raised more questions than it answered. If eels had reproductive organs, why did they never seem to use them in freshwater? Where were the males? The mystery deepened in 1876 when a young medical student named Sigmund Freud—yes, the future father of psychoanalysis—was tasked with locating male eel testicles. After dissecting hundreds of eels, Freud failed in his mission, adding his name to the long list of scientists thwarted by this slippery creature. The enigma of eel reproduction persisted well into the 20th century, when Danish researcher Johannes Schmidt finally traced the birthplace of European eels to the Sargasso Sea after a painstaking 18-year search. Yet even today, no human has ever observed eels breeding in the wild. This persistent mystery speaks to something profound about human knowledge: despite our technological advances, some aspects of nature continue to elude our understanding, humbling us with their secretiveness and reminding us that the natural world still holds secrets beyond our grasp.

Chapter 2: Metamorphosis: The Four Remarkable Life Stages

The European eel undergoes one of the most dramatic metamorphoses in the animal kingdom, transforming itself through four distinct life stages that make it seem like four entirely different creatures. The journey begins in the mysterious Sargasso Sea, where eggs hatch into transparent, leaf-shaped larvae called leptocephali. These strange creatures bear little resemblance to the adult eels they will become—flat and almost completely transparent, they look like tiny willow leaves drifting in the ocean currents. For up to three years, these delicate larvae are carried by the Gulf Stream across the Atlantic, traveling thousands of miles toward the coasts of Europe and North Africa. Upon reaching continental shelves, the leptocephali undergo their first metamorphosis, transforming into glass eels. As their name suggests, these eels remain transparent but take on a more recognizable eel-like form. About two to three inches long, glass eels are considered a delicacy in some cultures, particularly in Spain's Basque region. These young eels begin to swim actively against currents, making their way into estuaries and up rivers, demonstrating remarkable determination for creatures so small and seemingly fragile. Once in freshwater, glass eels transform again, developing pigmentation and becoming yellow eels. This is the longest phase of their life cycle, lasting anywhere from 5 to 20 years for males and 5 to 50 years for females. During this time, they grow muscular and adapt to a variety of habitats, from deep lakes to shallow streams and even swampy wetlands. Yellow eels are solitary, nocturnal hunters that burrow into mud during daylight hours and emerge at night to feed on small fish, frogs, insects, and virtually anything else they can find. The final and most dramatic transformation occurs when yellow eels become silver eels. Their eyes enlarge and turn blue for better vision in deep water, their digestive systems shut down, and their bodies accumulate fat reserves for the long journey ahead. Their coloration changes from yellowish-brown to silvery-blue, and their fins elongate for more efficient swimming. These physical changes prepare them for the immense journey back to the Sargasso Sea, where they will breed once and then die. This remarkable life cycle, with its multiple transformations across different environments, has no parallel among other migratory fish and represents one of the most extraordinary adaptations in the animal kingdom.

Chapter 3: Johannes Schmidt's Quest for the Sargasso Sea

In 1904, a determined young Danish biologist named Johannes Schmidt embarked on what would become one of the greatest scientific quests of the 20th century: to discover where European eels are born. Armed with little more than fine-meshed nets and unwavering persistence, Schmidt began methodically trawling the waters around Europe, collecting thousands of eel larvae and meticulously measuring them. His hypothesis was ingeniously simple yet brilliant: if he could find progressively smaller larvae, he could eventually trace them back to their birthplace. Schmidt's search took him farther and farther from European shores, across the treacherous waters of the Atlantic Ocean. The journey was fraught with obstacles. His research was interrupted by World War I, his funding was frequently in jeopardy, and one of his research vessels even sank. Yet Schmidt persisted with remarkable tenacity. He enlisted commercial vessels to help with his research, providing them with specialized nets and instructions to collect samples during their regular transatlantic voyages. This innovative approach allowed him to gather data from a much wider area than he could cover alone. After nearly two decades of searching, Schmidt's breakthrough finally came when he discovered the smallest, newly hatched eel larvae in an area of the western Atlantic known as the Sargasso Sea. This mysterious region, bounded by ocean currents rather than land and covered with floating sargassum seaweed, was an unlikely nursery for European eels. His discovery was revolutionary—it meant that European eels were born over 4,000 miles from the European rivers where they spend their adult lives, and that adult eels somehow navigate back to this specific area to spawn. Schmidt published his findings in 1923, fundamentally changing our understanding of eel biology and migration. His work stands as a testament to scientific perseverance and the value of systematic, methodical research in solving nature's most perplexing riddles. Though he never witnessed adult eels in the Sargasso Sea—indeed, no scientist has to this day—Schmidt's discovery provided the crucial missing piece in understanding the extraordinary life cycle of the European eel. His quest reminds us that some scientific discoveries require not just brilliant insight but also extraordinary patience and dedication spanning decades.

Chapter 4: Sigmund Freud and the Search for Eel Testicles

In a surprising intersection of natural science and psychological history, a 19-year-old Sigmund Freud—the future father of psychoanalysis—found himself in Trieste, Italy, in 1876, tasked with finding the elusive testicles of male eels. This peculiar assignment, given to him by his professor Carl Claus at the University of Vienna, was considered one of the most perplexing biological mysteries of the day. While female eels had been identified through their ovaries, male eels remained enigmatic, with no visible reproductive organs discovered despite centuries of examination. For nearly a month, young Freud diligently dissected hundreds of eels in a small laboratory near the Adriatic Sea. His dedication was remarkable—each day he would meet the fishermen at dawn to obtain fresh specimens, then spend hours carefully examining their internal anatomy under a microscope. In letters to his friend Eduard Silberstein, Freud described his work with both scientific precision and a touch of poetic frustration. "My hands are stained by the white and red blood of the sea creatures," he wrote, "all I see when I close my eyes is the shimmering dead tissue." Despite examining over 400 eels, Freud's search proved fruitless. He could not locate the male reproductive organs and was forced to conclude that his investigation was inconclusive. This early scientific failure contrasts sharply with the confident theoretical frameworks he would later develop in psychoanalysis. Some scholars have suggested that this experience with the mysterious, sexually ambiguous eel may have influenced Freud's later thinking about human sexuality and its hidden complexities. Interestingly, what Freud could not find was later discovered by another scientist. In 1896, Italian researcher Giovanni Battista Grassi finally identified male eels and explained why they had been so difficult to find: male eels develop testicles only during their final migration to the spawning grounds. The organs remain internal and undeveloped until the last stage of life, making them virtually impossible to detect in freshwater specimens. Freud's experience with the eel represents a fascinating historical footnote: how the quest to understand one of nature's most obscure mysteries briefly intersected with the early career of a man who would later dedicate his life to unraveling the mysteries of the human mind.

Chapter 5: Cultural Significance and Fishing Traditions

The European eel has woven itself into the cultural fabric of communities across the continent, creating traditions that have endured for centuries. On the Swedish "eel coast" in Skåne, a unique system of fishing rights called "åldrätter" dates back to the 16th century, when such rights were valuable enough to be purchased from archbishops and later redistributed by the Swedish king as rewards for loyalty. These fishing traditions created not just economic systems but entire ways of life, with specialized tools, techniques, and social practices passed down through generations. Eel fishing has historically been characterized by its small-scale, artisanal nature. Unlike industrial fishing, eel catching requires intimate knowledge of local waters and the eel's behavior. Traditional methods vary by region: in the Mediterranean, fishermen use elaborate systems of traps called "lavorieri"; in Ireland's Lough Neagh, long lines with hundreds of baited hooks are set from small boats; while in the Basque Country, glass eels are caught by hand with small nets on moonlit nights. These practices have created unique cultural identities in fishing communities, where specialized knowledge functions as a form of inheritance, connecting generations through shared expertise. The eel has also inspired rich culinary traditions across Europe. The "eel feast" or "gille" in southern Sweden features at least four different eel dishes, including smoked eel, fried eel, and specialties like "halmad eel" (baked in rye straw) and "luad eel" (salted and roasted on a spit). In London's East End, jellied eels were once a working-class staple, while in northern Italy, eel is the centerpiece of Christmas Eve dinner in many families. These culinary traditions reflect not just tastes but also the economic importance of a fish that was historically abundant, nutritious, and easily preserved. Today, these cultural traditions face an existential threat as eel populations decline dramatically. Many traditional fishermen have become advocates for conservation, arguing that their cultural heritage and the survival of the eel are inextricably linked. They suggest that without the cultural and economic incentive to care about eels—to catch, cook, and consume them—public interest in protecting them might wane. This creates a complex tension between preservation of cultural practices and conservation of a critically endangered species, highlighting how deeply intertwined human cultures and natural resources can become over centuries of coexistence.

Chapter 6: Navigating Home: How Eels Find Their Way

Perhaps the most astonishing aspect of the European eel's life is its remarkable ability to navigate across thousands of miles of open ocean to return to its birthplace in the Sargasso Sea. After spending years or even decades in the freshwater streams and lakes of Europe, mature silver eels embark on a journey that seems impossible for a creature without the benefit of maps, GPS, or even prior experience of the route. Yet somehow, they find their way back to a specific region of the western Atlantic Ocean with remarkable precision. Scientists have proposed several mechanisms that might explain this extraordinary feat of navigation. One leading theory suggests that eels possess a highly developed magnetic sense that allows them to detect and follow the Earth's magnetic field. The planet's magnetic patterns could serve as a kind of natural compass, guiding the eels across the vast expanse of the Atlantic. This theory is supported by experiments showing that eels can indeed sense magnetic fields and orient themselves accordingly, similar to how migratory birds navigate during long flights. Another hypothesis focuses on the eel's exceptional sense of smell. With olfactory abilities comparable to those of dogs, eels may be able to detect chemical signatures in the water that lead them back to their birthplace. Some researchers propose that eels might follow scent trails left by ocean currents or even detect the unique chemical composition of water from the Sargasso Sea. The eel's sensitivity to changes in water temperature and salinity might also provide navigational cues during their long migration. Recent tracking studies using electronic tags have revealed that the eel's journey is not as straightforward as scientists once thought. Individual eels take various routes across the Atlantic, sometimes swimming more than 30 miles per day, diving to depths of 3,000 feet during daylight hours (likely to avoid predators), and rising to warmer surface waters at night. While these studies have enhanced our understanding of eel migration patterns, they've also uncovered new mysteries. Most tagged eels disappear before reaching the Sargasso Sea, either falling prey to predators or shedding their tags. The final leg of their journey remains largely undocumented, preserving one last secret in the remarkable life cycle of this mysterious creature. What seems increasingly clear, however, is that eels may rely on a combination of navigational tools—magnetic sensitivity, olfaction, and perhaps even celestial cues—in what represents one of the most impressive feats of animal navigation on the planet.

Chapter 7: The Uncanny Eel in Literature and Psychology

The European eel has slithered its way into human imagination, inspiring a rich tapestry of literary works and psychological explorations that reveal our complex relationship with this mysterious creature. In literature, the eel often appears as a symbol of the unknown, the primordial, or the unconscious—a creature that exists at the boundary between the familiar and the strange. In Graham Swift's novel "Waterland" (1983), the eel becomes a central metaphor for history itself: slippery, elusive, and constantly moving between past and present, much like human memory and storytelling. German novelist Günter Grass created perhaps the most disturbing literary eel scene in his 1959 masterpiece "The Tin Drum." When the protagonist's pregnant mother witnesses eels crawling out of a horse's severed head, the grotesque image triggers a psychological breakdown that ultimately leads to her death. The scene powerfully illustrates what Sigmund Freud would call "the uncanny"—something simultaneously familiar and alien that disturbs our sense of reality. Indeed, Freud himself wrote about this concept in his 1919 essay "Das Unheimliche," arguing that the uncanny arises when something known becomes suddenly unfamiliar, creating a profound sense of discomfort. The connection between Freud and eels extends beyond literary theory. After his unsuccessful search for eel testicles as a young researcher, Freud turned his attention to human psychology. Some scholars have speculated that this early experience with a creature that conceals its sexuality may have influenced his later theories about repression and hidden desires. While such direct influence remains speculative, the parallel is intriguing—both in his scientific work and psychoanalytic theories, Freud sought to reveal what was hidden beneath the surface. The eel's disturbing quality in human psychology might be explained by its liminal nature—neither fully fish nor snake, neither fully aquatic nor terrestrial. In many cultures, creatures that transgress clear categories tend to provoke discomfort or even disgust. The eel's ability to transform itself through different life stages further disrupts our desire for stable classification. Even in contemporary society, the eel often elicits reactions of revulsion despite its culinary popularity in many regions. This contradiction reflects our ambivalent relationship with the mysterious and the unknown—simultaneously attracted to and repelled by that which we cannot fully comprehend or control, much like the deeper recesses of our own minds that psychoanalysis sought to illuminate.

Chapter 8: The Sixth Extinction: Why Eels Are Disappearing

The European eel, which has survived for over 40 million years through ice ages and continental drift, now faces its greatest challenge: human activity. Since the 1970s, the population of European eels has declined by more than 95%, placing this ancient species on the brink of extinction. This dramatic collapse is part of what scientists increasingly recognize as the "Sixth Extinction"—a mass die-off of species occurring at an unprecedented rate due to human influences, comparable to the five previous mass extinction events in Earth's history. Multiple factors contribute to the eel's decline, creating a perfect storm of threats. Physical barriers present perhaps the most visible problem. Hydroelectric dams and water management structures block migration routes, preventing young eels from reaching inland habitats and mature eels from returning to the sea. When silver eels attempt to pass through hydroelectric turbines during their seaward migration, mortality rates can reach 70% at a single facility. While fish ladders and bypasses exist for species like salmon, these rarely accommodate the unique swimming behavior of eels. Pollution presents another serious threat. As long-lived predators, eels bioaccumulate toxins in their tissues over decades. PCBs, pesticides, and heavy metals impair their reproductive development and energy storage capabilities, potentially preventing them from completing their long migration to the Sargasso Sea. Additionally, parasites introduced from Asia, particularly the swim bladder nematode Anguillicoloides crassus, have spread rapidly through European eel populations, weakening the fish and compromising their ability to regulate buoyancy during migration. Climate change may be delivering the final blow. Alterations in ocean currents could disrupt the transport of leptocephalus larvae from the Sargasso Sea to European coasts, while changes in temperature and salinity affect food availability during their oceanic drift. Meanwhile, commercial fishing continues to target eels at all life stages, with glass eel fishing particularly devastating due to high demand from Asian markets, where juvenile eels fetch astronomical prices for aquaculture operations. Conservation efforts face significant challenges, including the eel's complex life cycle spanning multiple jurisdictions and ecosystems. The European Union implemented an Eel Recovery Plan in 2007, but progress has been limited. Without coordinated international action addressing all threats simultaneously—from dam removal or bypass construction to pollution reduction, fishing restrictions, and climate change mitigation—the European eel may become the aquatic equivalent of the dodo, existing only in museum specimens and cultural memory. The potential loss of this ancient, mysterious creature would represent not just an ecological tragedy but the erasure of a living connection to the primordial past of our planet.

Summary

The European eel embodies one of nature's most profound paradoxes: a creature simultaneously common enough to have been served on dinner tables across Europe for centuries, yet mysterious enough that fundamental aspects of its biology remained unknown until recently. Through its remarkable life journey—from the Sargasso Sea to European waters and back again—the eel challenges our understanding of animal migration, adaptation, and survival. It reminds us that even in our age of technological advancement and scientific understanding, nature still harbors secrets that resist easy discovery. The eel's ability to transform itself multiple times throughout its life, navigating across thousands of miles of ocean to return to its birthplace, represents one of evolution's most extraordinary achievements. As we contemplate the precarious future of this ancient species, now critically endangered due to human activities, we might ask ourselves what other remarkable creatures and natural phenomena remain poorly understood or appreciated. How might our perception of the natural world change if we approached it with the same persistence and wonder that scientists like Johannes Schmidt brought to their study of the eel? The European eel's journey—both physical and within human cultural imagination—invites us to reconsider our relationship with the mysterious and the unknown. It suggests that true understanding requires not just scientific rigor but also patience, humility, and a willingness to accept that some aspects of nature may always retain an element of enigma, challenging us to expand our conception of what is possible in the living world.

About Author

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Patrik Svensson

Lars Patrik Svensson (born 1972) is a Swedish journalist and author. Svensson works in the cultural editorial department of Sydsvenskan and Helsingborgs Dagblad.In the summer of 2019, he made his debut as an author with the book Ålevangeliet, which is partly a non-fiction book about the eel as a species and about the eel's cultural history, and partly an autobiographical story about the author and his father. Rights to publish the book have been purchased in 2019 for publication in 33 other languages. The book received the August Prize for Swedish Non-Fiction Book of the Year 2019.

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