The Enduring Mystery of Eels: A Deep Dive into The Book of Eels
Few creatures have captivated human curiosity like the eel. Slippery, secretive, and seemingly otherworldly, the eel has puzzled scientists, inspired mythologies, and formed deep cultural and personal connections across generations. In The Book of Eels: Our Enduring Fascination with the Most Mysterious Creature in the Natural World, Patrik Svensson explores this enigmatic fish (yes, it is a fish) through a unique blend of science, history, and memoir.
Despite centuries of study, much of the eel’s life cycle remains a mystery. The book takes us on a journey from Aristotle’s incorrect theories to Sigmund Freud’s failed attempts to uncover the eel’s reproductive organs, and finally to modern conservation concerns as eel populations decline worldwide. At its core, The Book of Eels is not just about a fish—it is about the limits of human understanding, the relationship between science and storytelling, and the personal meaning we attach to the natural world.
The Science of the Eel: A Persistent Mystery
The European eel (Anguilla anguilla) and its American counterpart (Anguilla rostrata) have perplexed scientists for centuries. Unlike most fish, eels undergo an extraordinary transformation throughout their lifetime, passing through multiple stages of metamorphosis:
Leptocephalus (larval stage)
The eel’s life begins in the Sargasso Sea, a vast area of the Atlantic Ocean. The larvae are small, transparent, and leaf-shaped, drifting in ocean currents for years before reaching coastal waters.
Glass eel
As they approach freshwater, the larvae transform into small, clear, eel-shaped juveniles known as glass eels.
Yellow eel
Once they settle in freshwater rivers and lakes, they develop pigmentation and become known as yellow eels. In this phase, they can live for decades.
Silver eel
When they are fully matured, they undergo another transformation, their bodies turning silver as they prepare for a long journey back to the Sargasso Sea to spawn—a journey that scientists have never directly observed.
Despite modern advances in marine biology, no one has ever witnessed eels mating in the wild, and no scientist has ever found a mature eel with fully developed gonads in its natural habitat. This persistent mystery makes eels one of the most elusive creatures in science.
Historical Attempts to Solve the Eel’s Mystery
The eel’s enigmatic nature has inspired generations of thinkers to seek answers, from ancient philosophers to modern biologists. Throughout history, some of the greatest minds have tried—and failed—to solve the puzzle of eel reproduction. Their efforts, while often unsuccessful, have shaped the course of scientific inquiry and demonstrate humanity’s relentless pursuit of knowledge.
Aristotle and Spontaneous Generation
In ancient Greece, Aristotle was one of the first recorded scholars to study eels. Since he could not identify any reproductive organs in eels, he formulated the now-debunked theory that they must emerge spontaneously from mud. This idea, known as spontaneous generation, was a widely accepted belief in ancient times, as many natural phenomena were attributed to mystical forces. Aristotle's conclusions, though incorrect, reflected the scientific limitations of his era. His work laid the foundation for later thinkers to challenge and refine biological understanding. The idea of spontaneous generation persisted for centuries, as eels remained an elusive subject of study.
Sigmund Freud’s Eel Obsession
Before he became the father of psychoanalysis, Sigmund Freud was a young scientist searching for answers in the field of biology. In the late 19th century, he took on the challenge of studying eels, hoping to finally locate their reproductive organs and solve the long-standing mystery of their reproduction. Freud meticulously dissected hundreds of eels in an attempt to identify the presence of male reproductive organs. However, despite his exhaustive efforts, he came up empty-handed. The experience frustrated him, and he eventually abandoned biology for psychology. Some scholars have speculated that Freud’s early struggles with the elusive eel may have influenced his later theories about the unconscious mind—an unseen, enigmatic force shaping human behavior much like the hidden nature of eel reproduction.
Johannes Schmidt and the Sargasso Sea
The most significant breakthrough in eel research came in the early 20th century, when Danish marine biologist Johannes Schmidt embarked on an ambitious quest to trace the origins of the European eel. Over the course of several decades, Schmidt led numerous expeditions, collecting eel larvae from different parts of the Atlantic. By analyzing the size of the larvae, he was able to determine where they were youngest—and thus, where they must have originated. His research eventually pointed to the Sargasso Sea, a vast and mysterious region of the Atlantic Ocean near Bermuda, as the birthplace of European eels.
Schmidt’s findings were groundbreaking, yet they still left crucial questions unanswered. While he successfully identified the Sargasso Sea as the likely spawning ground, no scientist—including Schmidt himself—has ever witnessed eels actually mating there. Even today, no one has observed eels laying eggs, and the exact details of their reproductive process remain one of the greatest unsolved mysteries of marine biology.
Despite these uncertainties, Schmidt’s work provided the first solid scientific evidence of the eel’s transatlantic migration and laid the foundation for modern eel research. His painstaking efforts, conducted in an era without modern tracking technology, demonstrated the incredible dedication required to study one of nature’s most elusive creatures.
Eel Fishing as a Tradition
For the author, Svensson, eels are more than a scientific mystery—they are part of his personal history. He recalls childhood memories of fishing for eels with his father, a ritual that symbolized their bond. The eel becomes a bridge between generations, tying personal history to natural history.
The Decline of the Eel and Its Conservation
Today, eel populations are in crisis. Due to climate change, pollution, habitat destruction, and overfishing, their numbers have declined dramatically. Conservation efforts are hindered by the eel’s elusive nature—scientists still do not fully understand how they reproduce, making sustainable management difficult.
The decline of the eel serves as a warning about the impact of human activity on biodiversity. If we cannot protect a creature as resilient and long-lived as the eel, what does that say about our ability to safeguard other species?
The Eel as a Metaphor
Beyond its biological and historical significance, the eel serves as a symbol of the unknown. Svensson uses the eel as a metaphor for the limits of human knowledge, exploring how some mysteries—whether in science, philosophy, or life—may never be fully resolved.
By blending memoir, science, and storytelling, The Book of Eels challenges us to consider whether we should strive to solve every mystery or embrace the unknown as part of the human experience.
What The Book of Eels Teaches Us
At its heart, The Book of Eels is not just about a fish—it is about the human desire to understand the world around us. Through a blend of science, history, and memoir, Svensson presents the eel as a metaphor for the unknowable.
The book reminds us that, despite technological advances, nature still holds secrets beyond our grasp. It challenges us to consider how we relate to mystery—not just in science, but in our personal lives. And as eel populations decline, it serves as a call to protect what we do not yet fully understand.
Whether you are fascinated by biology, history, or philosophy, The Book of Eels offers a rich, thought-provoking read that lingers long after the last page.
What Do You Think?
Have you read The Book of Eels? What are your thoughts on the mystery of the eel and its deeper implications? Let’s discuss in the comments!
