Eels Alive!
In this episode of Stuff You Should Know, the hosts explore the biology and life cycle of eels, creatures that puzzled scientists for centuries. They discuss the distinctive anatomy and adaptations that allow eels to thrive in diverse environments, from shallow coastal waters to the deep ocean. The episode covers the historical mystery surrounding eel reproduction, which remained unsolved until the 20th century when researchers finally traced their breeding grounds to remote oceanic locations like the Sargasso Sea.
Beyond biology, the hosts examine eels' role in human history as both a nutritional staple and a form of currency in medieval societies. The episode also addresses the current conservation crisis facing eel populations, which have declined over 90% in recent decades due to factors including dams, overfishing, and glass eel harvesting for aquaculture. You'll come away with a deeper understanding of these mysterious fish and the environmental challenges threatening their survival.
This is a preview of the Shortform summary of the May 19, 2026 episode of the Stuff You Should Know
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1-Page Summary
Eel Biology and Adaptations
True eels belong to the order Anguilliformes, comprising 20 families, 111 genera, and over 800 species ranging from 4 inches to 12 feet. They share distinctive anatomical features including long, snake-like bodies and typically lack pelvic fins. Unlike most fish, eels propel themselves through wave-like undulations along their bodies rather than fin-based swimming, allowing them to move forward or backward with ease.
Eels are carnivorous hunters with smooth, mucus-coated skin that reduces friction and regulates water content. Moray eels, representing about 25% of all eels with roughly 200 species, are particularly notable. They lack opercula and must constantly open and close their mouths to breathe, creating a perpetual snarl appearance. Morays possess a dual-jaw system with sharp forward teeth and a rear pharyngeal jaw that drags prey into their throat. While not venomous, their mouth mucus contains toxins like hemagglutinin and crinotoxins that make bites dangerous. The ribbon eel, a striking moray species, exhibits hermaphroditism, beginning life as a blue-and-yellow male before transforming into an all-yellow female.
Some eels thrive in extreme environments. The gulper eel inhabits depths of 5,000 to 10,000 feet with an extendable jaw that scoops up scarce prey. Garden eels live in sandy burrows, filter-feeding on plankton while forming dense colonies. Eels undergo dramatic metamorphic transformations rather than simply growing, and they're thought to navigate using magnetite deposits in their heads that sense Earth's magnetic fields.
The Mystery of Eel Reproduction
The enigmatic life cycle of eels confounded scholars for millennia. Ancient Mediterranean and European civilizations never observed eels breeding, leading classical scholars to speculate about spontaneous generation from mud. Scientists struggled to locate reproductive organs until Italian surgeon Carlo Mondini identified eel ovaries in 1777. Finding male reproductive organs proved even harder—Sigmund Freud personally dissected 401 eels before succeeding on his final specimen.
Observers eventually recognized that transparent "glass eels" arrived in coastal waters each spring, transforming into "elvers" and then maturing into yellow eels inhabiting freshwater. As they aged, eels transformed into "silver eels" with developed reproductive organs, preparing for a final spawning journey.
Early biologists noticed small, leaf-shaped larvae called Leptocephalus brevirostris drifting in the plankton, mistakenly classifying them as a separate species. In the late 19th century, Yves Delage witnessed these larvae metamorphose into glass eels, establishing their true identity and linking oceanic larvae with riverine adults.
Danish marine biologist Ernst Johann Schmidt, backed by the Carlsberg Foundation, led early 20th-century expeditions to find the breeding grounds. By collecting larvae across the Atlantic, Schmidt observed that the smallest were always found in the Sargasso Sea, suggesting this remote region was the spawning site. In 2018, Rosalind Wright and European scientists confirmed Schmidt's hypothesis using tracking tags. The Sargasso Sea's warm, saline, still waters within a gyre create ideal breeding conditions. Different eel species spawn in specific locations—Japanese eels near the Mariana Ridge, African longfin eels in the Indian Ocean.
Mature silver eels migrate from rivers across the Atlantic to breed in the Sargasso Sea. Their larvae drift back to Europe as glass eels, then swim upstream to freshwater habitats, making eels anadromous—living in freshwater but reproducing in the ocean.
Eels as Food and Currency
American, European, and Japanese eels have played remarkable roles as nutrition sources and even currency. In northeastern North America, eels accounted for over a quarter of all fish species. Indigenous peoples harvested eels using willow traps and preserved them by smoking or salting for storage and travel. Europeans developed similar preservation methods.
Eels provided exceptional nutritional value, rich in protein and vitamins B12, A, and D. A fillet contains about 375 calories, making eels one of the most nutritious and calorie-dense foods available. In medieval England, about half a million dried eels paid rent annually, with eels counted in units called "sticks" (ten eels) and "binds" (twenty-five eels), functioning as standardized currency.
During medieval Christian fasting periods lasting up to 120 days annually, church law allowed fish but not meat. Eels became favored meals, partly because their mysterious reproduction made them seem asexual and pure. In Japan's Edo period, unagi became one of four great foods. Raw eel blood is toxic, so unagi is always cooked before serving, often coated with kabayaki sauce before grilling.
Eel Population Collapse
American and European eel populations have dropped over 90% since the 1970s, with similar declines in Japanese eels. The IUCN lists European eels as critically endangered and American, Japanese, and New Zealand longfin eels as endangered. Dams and hydropower turbines block essential migrations and kill migrating eels. Glass eel harvesting removes juveniles before they can mature and reproduce, preventing population recovery.
Additional factors include overfishing, wetland loss, and pollution. Eel reproduction in captivity remains highly challenging—farmers must use hormones to induce sexual development, and maintaining larvae alive proves extremely difficult. Nearly all consumed eels come from aquaculture facilities using wild-caught glass eels. In Maine, the United States' only glass eel fishery, 425 licensed harvesters called Elvermen collect around 7,500 pounds annually, mostly shipped to Hong Kong for aquaculture, exerting significant pressure on already dwindling wild populations.
1-Page Summary
Additional Materials
Counterarguments
- While eels are described as anadromous (living in freshwater but reproducing in the ocean), the term "catadromous" is more accurate for eels, as they primarily live in freshwater and migrate to the sea to spawn.
- The statement that "nearly all consumed eels come from aquaculture using wild-caught glass eels" could be nuanced by noting that some regions still rely on wild-caught adult eels for direct consumption, though this is a minority compared to aquaculture.
- The claim that eels can swim backward with ease is true for some species, but not all eels exhibit the same degree of backward swimming ability.
- The assertion that eels were favored during medieval Christian fasting periods "because their mysterious reproduction made them seem asexual and pure" may oversimplify the reasons; practical availability and church classification of eels as "fish" were also significant factors.
- The idea that eel population declines are primarily due to dams, overfishing, and glass eel harvesting could be broadened to acknowledge that climate change and oceanic changes may also play important roles, as suggested by some recent studies.
Actionables
- you can create a personal eel migration tracker by marking a world map with the known migration routes and spawning grounds of different eel species, then use colored pins or stickers to visualize how far these animals travel and reflect on the challenges they face, helping you appreciate the complexity of their life cycle and the importance of habitat connectivity.
- a practical way to support eel conservation is to choose seafood alternatives to eel when dining out or shopping, and keep a simple note on your phone or wallet listing sustainable options, so you can make informed choices that reduce demand for wild-caught glass eels and help protect endangered populations.
- you can design a home experiment to observe how water flow and obstacles affect movement by filling a bathtub or large container with water, placing objects like tubes or mesh to simulate dams, and using toy fish or objects to mimic eel movement, giving you hands-on insight into the migration barriers eels encounter.
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Eel Biology: Structure, Species, Swimming, and Adaptations
Eels Belong To Anguilliformes, Encompassing Diverse Families and Species
To truly qualify as an eel, an animal must belong to the order Anguilliformes. Unlike misnamed species like electric eels and sea snakes, which do not belong to this group, “true” eels make up a remarkable order comprising 20 families, 111 genera, and more than 800 species. Their sizes vary dramatically, ranging from just 4-inch long species to giant moray eels that can reach up to 12 feet.
Eels share several anatomical features. They have long, snake- or worm-like bodies and typically lack pelvic fins—a feature absent in their evolutionary development. Many do not have pectoral fins, although some species possess a dorsal fin along their back. This streamlined structure makes them easily recognizable as they move through water.
Eels Use Wave-Like Contractions for Unique Locomotion Instead Of Fin-based Swimming
Eels are distinctive swimmers. Lacking the fin-based locomotion common to most fish, eels propel themselves by generating wave-like undulations that travel along their bodies. These neuromuscular contractions not only speed them forward but, through simple reversal of the wave pattern, allow eels to swim backward with ease. Some sources note that eels even make a beeping sound when moving in reverse. This undulatory swimming compensates for their lack of significant fin structures and allows them to “slither” gracefully through aquatic environments.
Eels Have Specialized Features for an Aquatic, Predatory Lifestyle
Eels’ smooth, slippery skin is coated in a protective mucus layer. This mucus reduces friction, allowing for more efficient swimming, and has the added function of regulating bodily water content. Eels are carnivorous hunters, preying primarily on other fish species. Their predatory adaptations are crucial for survival across the diverse habitats they occupy.
Moray Eels: Significant Ocean Subfamily With Distinctive Adaptations
Among the various eel families, moray eels are particularly noted for their ocean-dwelling habits and striking appearance. Comprising 15 genera and about 200 species—roughly 25% of all eels—morays typically dwell inside crevices in coral reefs, coming out mostly at night.
Moray eels lack opercula, the bony covers that most fish use to move water across their gills. As a result, they must constantly open and close their mouths to pass water through their gills, giving them the appearance of baring their teeth in a perpetual snarl. Moray eels are equipped with a dual-jaw system: their forward-facing jaw has very sharp teeth capable of delivering deep, painful bites, while a rear, backward-facing pharyngeal jaw locks prey in place and drags it further into the throat. Although morays are not venomous, their bites are dangerous due to toxins in their mouth mucus—substances like hemagglutinin, which clumps red blood cells, and crinotoxins, which destroy them. These factors can make wounds from moray bites severely painful and prone to infection.
Ribbon Eel: A Hermaphroditic Moray Eel Starting As Blue-Yellow Male, Becoming All-yellow Female, Reproducing As Either Sex
One of the most visually striking members of the moray family is the ribbon eel. Ribbon eels begin life as blue-and-yellow males and, as they mature, can change into all-yellow females—a rare example of hermaphroditism among eels. Depending on their life stage, ribbon eels are able to reproduce as either sex and display fluorescent colors that stand out in reef environments.
Eels Evolve to Survive Extreme Deep-Sea Environme ...
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Eel Biology: Structure, Species, Swimming, and Adaptations
Additional Materials
Counterarguments
- The statement that "eels produce a beeping sound when swimming backward" is not widely supported in scientific literature; there is little to no credible evidence that eels make such a sound during locomotion.
- While moray eels lack traditional opercula, they do possess reduced gill covers; the description may overstate the absence of this anatomical feature.
- The assertion that all ribbon eels are hermaphroditic and always change from male to female may oversimplify their reproductive biology, as not every individual necessarily completes this transition.
- The idea that eels "likely use magnetite deposits in their heads to sense Earth's magnetic fields" ...
Actionables
- You can practice eel-inspired movement exercises to improve flexibility and body awareness by mimicking wave-like undulations and backward motions, helping you explore new ways to move and stretch at home or in the pool.
- A practical way to boost your observation skills is to visit an aquarium or watch underwater videos and try to identify different eel species based on their body shapes, fin placement, and coloration, keeping a personal log of your findings.
- You can create a simple home experiment to ...
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Eel Life Cycle: The Mystery and Discovery Of Breeding In the Sargasso Sea
The enigmatic life cycle of eels has confounded scholars for millennia, with the question of how and where eels reproduce forming one of the great riddles of natural history. The eventual solution, placing their mysterious breeding ground in the Sargasso Sea, marks a triumph of persistent scientific observation and evidence.
Incorrect Theories on Eel Reproduction Proposed by Ancient Scholars
Eel Reproduction Long a Mystery To Mediterranean and European Civilizations
Since antiquity, eels baffled the Mediterranean and European civilizations. No one saw eels laying eggs or breeding—adult eels simply seemed to appear. This absence of observable reproduction led thinkers to wild ideas.
Classical Theories: Spontaneous Generation to Eels From Mud
Lacking evidence, classical scholars speculated that eels arose spontaneously from mud or even generated themselves. The exact mechanism was unknown and heavily debated, but the dominant impression was that eels did not reproduce in any typical animal fashion.
Scientists Struggled to Locate Eel Reproductive Organs
Eel Ovaries First Identified by Carlo Mondini, 1777
Confusion persisted well into the Enlightenment. Scientists dissected eels repeatedly without finding reproductive organs, further fueling legends of mysterious generation. In 1777, Italian surgeon Carlo Mondini finally located eel ovaries, although others struggled to replicate this discovery for decades.
Freud Dissected 401 Eels to Find Male Reproductive Organs, Showing Scientific Persistence
The search for male reproductive organs proved even more daunting. Sigmund Freud, before his fame as a psychoanalyst, personally dissected over 400 eels in pursuit of testes and succeeded on the 401st specimen, exemplifying scientific resolve in the face of ambiguity.
Scientists Unraveled Eel Life Cycle Through Decades of Observation
Glass Eels Are Juvenile Transparent Eels Appearing In Coastal Waters Each Spring Before Developing Into Elvers and Maturing Into Yellow Eels Inhabiting Freshwater Rivers and Streams
Observers eventually recognized that juvenile, transparent “glass eels” arrived in coastal waters each spring. These young eels, virtually transparent, transformed into darker, adolescent “elvers,” then matured into yellow eels living in rivers and streams, a prized catch.
Eels Become Silver Eels With Developed Reproductive Organs Before Their Journey to Spawning Grounds
As eels aged, they traveled downstream and gradually transformed again into “silver eels,” developing reproductive organs and preparing for a final journey to distant spawning grounds.
Misidentified Fish Species Recognized As Eel Larvae
Leptocephalus Brevirostris, Once Thought a Distinct Species, Was Observed by Yves Delage to Metamorphose Into a Glass Eel
Early marine biologists noticed small, willow leaf-shaped larval fish called Leptocephalus brevirostris drifting with the plankton. These were mistakenly classified as a separate species. In the late 19th century, Yves Delage kept leptocephalus larvae in a tank and directly witnessed them metamorphose first into glass eels, then elvers, establishing their true identity as the eel’s larval form. Giovanni Battista soon confirmed this transformation in the wild.
Eel Larvae Discovery Bridges Ocean and Freshwater Populations
This revelation linked oceanic larvae with riverine adult eels, meaning eels were not spontaneously generated but underwent a complex metamorphosis and migration.
Ernst Schmidt, Backed by Carlsberg Foundation, Led an Expedition to Find the Eel Spawning Ground
Schmidt Partnered With Vessels to Collect Larvae and Observe Size Patterns
The remaining mystery was the location of the breeding grounds. Danish marine biologist Ernst Johann Schmidt, with support from the Carlsberg Foundation, led expeditions in the early 20th century to answer this riddle. Schmidt and collaborating commercial fishing vessels collected eel larvae (leptocephali) from various parts of the Atlantic, tracking their size and distribution.
Eels Reproducing In the Sargasso Sea
Schmidt observed that the smallest larvae were always found far out in the central Atlantic, in the Sargasso Sea, suggesting that this remote expanse was the spawning site. Though Schmidt never directly witnessed eels breeding ther ...
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Eel Life Cycle: The Mystery and Discovery Of Breeding In the Sargasso Sea
Additional Materials
Counterarguments
- While the Sargasso Sea is widely accepted as the primary spawning ground for Atlantic eels, direct observation of actual spawning events in the wild remains extremely rare, and some aspects of their reproductive behavior are still not fully understood.
- The identification of eel reproductive organs was challenging due to their seasonal development, which may have contributed to the historical confusion rather than a lack of scientific rigor.
- Although the spontaneous generation theory was incorrect, it reflected the limitations of observational tools and scientific knowledge available to ancient scholars, rather than a lack of critical thinking.
- The anadromous classification of eels is sometimes debated, as some definitions ...
Actionables
- you can keep a curiosity journal to document everyday mysteries or unexplained phenomena you notice, then periodically revisit your entries to brainstorm possible explanations or research updates, mirroring the centuries-long quest to solve natural puzzles.
- a practical way to challenge assumptions is to pick a common belief or "obvious" fact in your daily life and investigate its origins, looking for overlooked evidence or alternative explanations, just as early thinkers questioned how eels reproduced.
- you can crea ...
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Eels: Significance as Food and Currency in Medieval Europe, Japan, and Indigenous North America
Eels, specifically the American eel, European eel, and Japanese eel, play a remarkable role in human history as sources of nutrition, cultural tradition, and even currency. These freshwater eels spawn in the ocean but live most of their lives in rivers and streams and have been deeply important for centuries across multiple continents.
Eels: A Key Protein for Indigenous Northeast Americans and Europeans
In coastal streams of northeastern North America, eels accounted for more than a quarter of all fish species. Indigenous peoples prized eel for its abundance and versatility. They harvested eels using traps, often woven from willow, that were easy for eels to enter but difficult to exit. Once caught, eels were smoked or salted, which allowed them to be preserved, carried on long journeys, or stored for use when fresh food was scarce. Grilling was also a common preparation method.
European populations shared a similar enthusiasm for eel, developing methods like smoking, salting, and drying to preserve this resource. Archaeological evidence of eel traps in Europe attests to its long-standing value. Smoked, salted, or dried eel became a staple food, especially in places where storing meat was challenging.
Eels Offered Exceptional Nutritional Value, Making Them a Valuable Food Source
Eels provided a dense nutritional profile critical for survival, especially in times with limited access to other proteins or nutrients. Eel flesh is rich in protein as well as vitamins B12, A, and D. These nutrients were vital in eras when dietary diversity was limited and vitamin D, in particular, was rare for people without regular sun exposure. An eel fillet contains about 375 calories, offering a substantial source of calories, beneficial fats, and proteins. This made eel one of the most nutritious and calorie-dense foods available, benefiting populations in both the Old and New Worlds.
Eels Were Medieval Currency For Taxes and Debts
Beyond food, eels also functioned as a form of currency, especially in medieval England, where about half a million dried eels were used to pay rent annually. Eels were counted in denominations: a "stick" consisted of ten eels, while a "bind" was twenty-five. These units allowed eels to serve as standardized payment for rents, taxes, and even debts, acting much like denominations of money.
Eels in Medieval Christian and Catholic Fasting Traditions
Church law in medieval Europe restricted the consumption of meat during fasting seasons lasting up to 120 days a year, but allowed fish. Because eels were plentiful, they became a favored meal during these long periods when meat was forbidden. Another reason eels specifically were suitable for fasting is their reputation for being asexual—since people did not understand their reproduc ...
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Eels: Significance as Food and Currency in Medieval Europe, Japan, and Indigenous North America
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Counterarguments
- While eels were important in some regions, their significance as a staple food or currency was not universal across all of Europe, North America, or Japan; many cultures and regions did not rely on eels to the same extent.
- The nutritional value of eel is high, but eels were not always accessible to all populations due to geographic, seasonal, or ecological limitations.
- The use of eels as currency in medieval England was notable but relatively localized and did not replace coinage or other forms of payment on a broad scale.
- The belief that eels were asexual and thus symbolically pure for fasting was based on a misunderstanding of their biology, reflecting historical misconceptions rather than factual knowledge.
- The prominence of unagi in Edo-period Japan was significant, but eel consumption was often limited by cost and availability, making it a luxury food for many rather than a s ...
Actionables
- you can create a personal nutrition tracker to compare the nutritional value of foods you eat with that of eel, helping you identify and incorporate more nutrient-dense options into your meals for better health and energy.
- a practical way to explore historical food preservation is to try adapting modern kitchen tools to replicate ancient preservation techniques, such as using a dehydrator or low-temperature oven to make your own preserved fish snacks for travel or emergency supplies.
- you can design a themed meal night where you ...
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Eel Populations Plummet 90% Since 1970s: Dams, Overfishing, Habitat Loss Blamed
Eel Populations Globally Have Faced Catastrophic Declines Over Fifty Years Due to Multiple Threats
American and European eel populations have dropped by more than 90% since the 1970s, a pattern echoed by Japanese eel populations. The International Union for Conservation of Nature (IUCN) now lists European eels as critically endangered, while American, Japanese, and New Zealand longfin eels are classified as endangered. This dramatic collapse results from a combination of environmental and human-driven pressures.
Dams and Water Infrastructure Collapse Eel Populations
Dams and other water infrastructure have had a massive negative impact on eel populations. Hydropower turbines and dams block essential eel migrations to the Sargasso Sea, where reproduction occurs. Beyond forming impassable barriers, turbines at hydro facilities kill migrating eels, further disrupting their complex life cycle and decimating populations.
Overfishing of Glass Eels Prevents Population Recovery
Glass eels—the juvenile form of eels—are intensely harvested from the wild and transferred to farms to be raised to maturity for consumption. This practice removes the very cohort essential for population recovery. By capturing glass eels before they can mature and reproduce, fisheries prevent replenishment of wild populations. Since most eel larvae perish before reaching this stage, removing those that survive further decimates stocks, causing catastrophic population decline.
Environmental Factors Contribute To Eel Decline Across Habitats
Other major factors contributing to eel decline are overfishing, wetland loss, and pollution. Wetland loss eliminates crucial habitats for juvenile eels, and polluted waters degrade the quality required for eel survival and migration. These cumulative pressures compound the decline, making it harder for eel populations to recover.
Most Human-Consumed Eels Come From Aquaculture Facilities Raising Captured Glass Eels
Eel reproduction in captivity remains highly challenging and unreliable. Farmers must induce sexual development using hormones because natural breeding rarely occurs in cages or tanks. Even when breeding is induced, maintaining eel larvae alive in captivity proves extremely difficult, as the larvae require specific organic matter and ocean conditions typically found only in the wi ...
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Eel Populations Plummet 90% Since 1970s: Dams, Overfishing, Habitat Loss Blamed
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Clarifications
- Glass eels are the transparent, juvenile stage of eels after they hatch from eggs in the ocean. They migrate from the sea to freshwater or coastal habitats where they grow into adult eels. This stage is crucial because it represents the transition from ocean larvae to the habitats where eels mature and reproduce. Protecting glass eels ensures future generations and the continuation of the eel life cycle.
- The Sargasso Sea is the unique spawning ground for several eel species, including American and European eels. It is located in the North Atlantic Ocean and is characterized by floating seaweed called Sargassum, which provides a habitat for eel larvae. After hatching there, eel larvae drift with ocean currents back to coastal freshwater habitats where they grow. This migration cycle is essential for eel reproduction and population sustainability.
- Eel larvae, called leptocephali, feed on marine snow—tiny organic particles and plankton drifting in the ocean. They require stable temperature, salinity, and ocean currents to access these food sources and complete their long migration. These precise conditions are difficult to replicate in captivity, making larval survival challenging. Without this natural environment, larvae cannot grow or develop properly.
- Eels have a complex reproductive cycle triggered by environmental cues absent in captivity. Hormones like gonadotropins are injected to stimulate gonad development artificially. This hormonal induction mimics natural signals to initiate maturation and spawning. However, timing and dosage are critical and difficult to optimize, making breeding unreliable.
- Hydropower turbines generate electricity by using flowing water to spin blades inside the turbine. Eels migrating upstream or downstream must pass through these turbines, where the fast-moving blades can injure or kill them. The physical structure of dams also blocks eels from reaching their breeding or feeding grounds. This disruption reduces eel survival rates and hinders their life cycle completion.
- Elvermen are specialized fishermen licensed to harvest glass eels, also called elvers, during their migration. They use nets or traps in rivers and estuaries to catch these juvenile eels as they move upstream from the ocean. Their work is crucial for supplying glass eels to aquaculture but also directly impacts wild eel populations. The term "Elvermen" specifically refers to this group involved in the early-stage eel fishery.
- Most eel larvae drift thousands of miles in ocean currents, facing predators and harsh environmental conditions. Their tiny size and limited energy reserves make survival difficult during this long migration. Additionally, changes in ocean temperature and pollution can reduce larval survival rates. These factors combine to cause high mortality before larvae reach the ...
Counterarguments
- While eel populations have declined significantly, some localized management efforts (such as fishing quotas, seasonal closures, and habitat restoration) have shown signs of stabilizing or modestly increasing eel numbers in certain regions.
- The impact of dams and hydropower on eel migration varies depending on the presence of mitigation measures like fish ladders or eel passes, which can partially restore migratory routes.
- Not all aquaculture operations rely exclusively on wild-caught glass eels; there are ongoing research and pilot projects aimed at closing the eel life cycle in captivity, which could reduce future pressure on wild stocks.
- The Maine glass eel fishery is regulated with strict quotas, licensing, and monitoring to limit ...
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1-Page Summary- Eel Biology: Structure, Species, Swimming, and Adaptations
- Eel Life Cycle: The Mystery and Discovery Of Breeding In the Sargasso Sea
- Eels: Significance as Food and Currency in Medieval Europe, Japan, and Indigenous North America
- Eel Populations Plummet 90% Since 1970s: Dams, Overfishing, Habitat Loss Blamed
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